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About:config entries

From MozillaZine Knowledge Base

(Redirected from About:config Entries)

This is not the place to edit your configuration settings. This is a reference to the entries in about:config, where all user preferences can be viewed and modified. In most cases the list below doesn't state whether a given preference applies to all, or only some (and which), of Firefox, Thunderbird, Mozilla Suite, SeaMonkey, or even the now discontinued Sunbird: trial and error is often the only way to tell if some particular preference applies to your version of your application.

Users not already familiar with about:config entries should read the companion article, about:config, which describes how to modify values and work with the about:config list.

This article does not contain a complete list of all preferences. If you don't find an entry below for a given preference, check the Category:Preferences (multiple-page) listing, which includes many new preferences that have not been added here, as well as those preferences that have been migrated from sections of this article. Also check Mail and news settings for a listing of Thunderbird and Mozilla Suite/SeaMonkey mail and news preferences. Alternative lists can be found here:

(For a comparison view of table and actual about:config settings, use the Fox Splitter (formerly Split Browser) extension or the new version of Fox-Splitter to show one above the other. Also, finding item documentation for a preference from within about:config can be sped up with the Prefsearch extension, which adds a context menu item to search Google for the selected preference item.)

Note: There is no indication in the table as to which items will take effect immediately, with a new window, or require restarting.

Spaces between the dots in preference names on this page exist purely for word-wrapping. They are actually not present and should not be thought as so. Editors of this page must take care to follow this convention in order to not force users to horizontally scroll this article.

Contents

Accessibility.

accessibility.* allows you to modify Find As You Type behavior, change how the [Tab] key works in web pages and XUL, turn on caret browsing, and tweak other accessibility-related features.

accessibility.* has been migrated to Category:Preferences.

Advanced.

advanced contains two prefs: Advanced.mailftp and Advanced.system.supportDDEExec.

advanced.* has been migrated to Category:Preferences.

Alerts.

alerts. contains three prefs, all related to the GUI: Alerts.slideIncrement, Alerts.slideIncrementTime, and Alerts.totalOpenTime.

alerts.* has been migrated to Category:Preferences.

App.

app.* allows you to modify application update behaviour.

app.* has been migrated to Category:Preferences.

Bidi.

Name Type Meaning of Values
bidi. browser. ui Boolean True: Activates bidi interface and keyboard unconditionally
False: Only activates bidi interface and keyboard in bidi locales. (Default)
bidi. characterset Integer How the browser determines the character set to use
1 (default): Document-specified character set
2: Default character set
bidi. controlstextmode Integer How controls are used
1 (default): Logical
2: Visual (this is no longer supported and leads to strange side-effects, see bug 373319)
3: Container
bidi. direction Integer Select direction of text
1 (default): Left-to-right
2: Right-to-left
bidi. numeral Integer How numerals are displayed
0 (default): Nominal numerals
1: Regular context numerals
2: Hindi context numerals
3: Arabic numerals
4: Hindi numerals
bidi. support Integer Select provider of bi-directional support
1 (default): Mozilla
2: OS
3: Disable
bidi. texttype Integer Type of text
1 (default): Charset
2: Logical
3: Visual
bidi.edit.caret movement style
bidi.edit.delete immediately

Browser.

Name Type Meaning of Values
browser. active_color String The default color for active links as a hex code. Default is #EE0000.
browser. anchor_color String The default color for links as a hex code. Default is #0000EE
Note: This can be changed in Firefox via "Tools → Options → Content / Fonts & Colors → Colors... → Link Colors → Unvisited Links" (Firefox 1.5 and above) and via "Edit → Preferences → Appearance → Colors / Link Colors → Unvisited Links" in Mozilla Suite and SeaMonkey.
browser. backspace_action Integer Determines the behavior of the backspace key
0: Goes back in history
1: Acts as Page Up
2 (and above): Does nothing
Note: See bug 301248 (Mozilla Suite)
browser. blink_allowed Boolean True (default): Use of the blink tag or CSS's text-decoration: blink will result in blinking elements.
False: Blinking is disabled.
browser. block. target_new_window Boolean True: Links with target set to _blank will open in the current tab instead of a new window.
False: Links with target set to _blank will open in a new window.
Note: No longer in use. Use browser.link.open_newwindow instead.
browser. bookmarks. added_static_root Boolean Keeps track of whether a root folder for system (imported) bookmarks has been created in bookmarks.html.
True: The root folder has been created
False (default until import complete): Create the root folder (unless we're using dynamic bookmarks - browser.bookmarks.import_system_favorites), and then set this pref to true.
browser. bookmarks. file String The full path and filename of your bookmarks file (bookmarks.html). In Windows, the path separator must be two backslashes (e.g. "C:\\Path\\To\\bookmarks.html") if the value is being set in user.js or prefs.js instead of within about:config
browser. bookmarks. import_system_favorites Boolean Determine the system bookmark strategy.
True: Enable a "live view" of system bookmarks which is read-only
False (default): Opposite of above.
Note: Setting this to "true" will prevent "Imported IE Favorites" folder from being deleted where applicable (see bug 22642).
browser. bookmarks. livemark_refresh_seconds Integer The number of seconds between Live Bookmark checks. Values under 60 are assumed to be 60; the default is 3600 (1 hour).
browser. bookmarks. restore_default_bookmarks Boolean True: Overwrite the current bookmarks.html file with the default set of bookmarks.
False (default): Do not reset bookmarks.
Note: Firefox 1.5 and above only
browser. bookmarks. sort. direction String The order in which to sort bookmarks in the Bookmarks Manager
descending (default): Unsorted
natural: Alphabetically, A-Z
ascending: Alphabetically, Z-A
Note: In Firefox, this can be changed via "Bookmarks → Organize (or Manage) Bookmarks... → View"
browser. bookmarks. sort. resource String The RDF source to use when sorting the bookmarks in the Bookmarks Manager
rdf:http://home.netscape.com/NC-rdf#Name (default) - by bookmark name
rdf:http://home.netscape.com/NC-rdf#URL - by URL
rdf:http://home.netscape.com/NC-rdf#ShortcutURL - by bookmark keyword
rdf:http://home.netscape.com/NC-rdf#Description - by description
rdf:http://home.netscape.com/NC-rdf#BookmarkAddDate - by bookmark creation date
rdf:http://home.netscape.com/WEB-rdf#LastModifiedDate - by bookmark modification date
rdf:http://home.netscape.com/WEB-rdf#LastVisitDate - by date of last visit

Note: In Firefox, this can be changed via "Bookmarks → Organize (or Manage) Bookmarks... → View"

browser. cache. check_doc_frequency Integer How often to check the remote page for a newer version than what might be in the cache
0: Check once per browser session
1: Check every time I view the page
2: Never check (always use cached page)
3 (default): Check when the page is out of date (automatically determined)
browser. cache. disk. capacity Integer Amount of disk space allowed for the browser's cache (in KB). Default is 50000.
Note: In Firefox, this can be changed via "Tools → Options → Advanced → Network / Offline Storage" (Firefox3), Tools → Options → Advanced → Network / Cache" (Firefox 2) or "Tools → Options → Privacy → Cache (Firefox 1.5 and earlier); in Mozilla Suite/SeaMonkey, via "Edit → Preferences → Advanced → Cache".
browser. cache. disk. enable Boolean True (default): Use disk cache, up to capacity specified in browser.cache.disk.capacity
False: Disable disk cache (same effect as setting browser.cache.disk.capacity to 0)
browser. cache. disk. parent_directory String Full path to the parent directory of the Cache folder used for storing the browser's cache. In Windows, the path separator must be two backslashes (e.g. "C:\\Path\\To\\Parent\\Folder") if the value is being set in the user.js or prefs.js instead of within about:config.
browser. cache. disk_cache_ssl Boolean True (default): Cache content received via SSL
False: Do not cache content received via SSL
Note: See bug 531801 for more information
browser. cache. memory. capacity Integer Determines how the browser uses RAM for cache.
-1 (default): Automatically set size of capacity as a percentage of physical RAM
0: disables the memory cache device entirely
(n): Set the maximum RAM used to n KB.
browser. cache. memory. enable Boolean True (default): Use memory cache, up to capacity specified in browser.cache.memory.capacity (if set); otherwise, use a percentage of physical RAM (see bug 105344)
False: Disable memory cache (same effect as setting browser.cache.memory.capacity to 0)
browser. chrome. favicons Boolean True (default): Load and display "favicons" residing in the current page's site root directory
False: Opposite of the above
Note: This should be set to the same value as browser.chrome.site_icons for legacy reasons.
browser. chrome. image_icons. max_size Integer If an image's height or width is greater than this number (in pixels), the image will not have a thumbnail placed in its tab (or the Location Bar). Setting it to 0 will prevent thumbnails from being used altogether. The default value is 1024 pixels.
Note: Firefox 1.5 and above and SeaMonkey only.
browser. chrome. load_toolbar_icons Integer 0 (default): Never load site icons/favicons when displaying bookmarks in menus (overrides browser.chrome.site_icons)
1: Load site icons/favicons when they've been cached
2: Always load site icons/favicons
browser. chrome. site_icons Boolean True (default): Load and display site icons specified by link element(s) in the web page
False: Opposite of the above
Note: This should be set to the same value as browser.chrome.favicons for legacy reasons.
browser. chrome. toolbar_style Integer Set toolbar style for browser
0: Pictures Only
1: Text Only
2 (default): Pictures and Text
browser. chrome. toolbar_tips Boolean Determines tooltip behavior for chrome elements.
True (default): Show tooltips for toolbars and bookmarks. Display the name and URL for bookmarks
False: Hide tooltips for chrome elements
browser. chromeURL String Location of browser's UI chrome; launched at browser startup. Default value is chrome://browser/content/
browser. display. background_color String The default color for the background of browser content as a hex code. This affects blank tabs, web pages whose backgrounds are not explicitly set, and XUL error pages. Default value is #FFFFFF.
Note: In Firefox, this can be changed via "Tools → Options → Content / Fonts & Colors → Colors... → Text and Background → Background " (Firefox 1.5 and above).
browser. display. focus_background_color String The default color for the background of focused elements as a hex code. Default value is #117722. Requires that browser.display.use_focus_colors be true
browser. display. focus_ring_on_anything Boolean True: Display the focus ring (normally only shown on links) on anything
False (default): Display the focus ring on links only
browser. display. focus_ring_width Integer Determines the display of the focus ring around focused elements.
0: Hide focus ring
1 (default): Dots around focused elements will be displayed with a 1 pixel border
(n): Display dots with a width of n pixels around focused elements
browser. display. focus_text_color String The default color for the text of focused elements as a hex code. Default value is #ffffff. Requires that browser.display.use_focus_colors be true
browser. display. force_inline_alttext Boolean True: Force broken images' alt text to be displayed inline
False (default): Show an icon if rendering in Quirks Mode and there is no alt text, or if rendering in Quirks Mode and the image has a size specified.
browser. display. foreground_color String The default color for the foreground of browser content as a hex code. This affects web pages whose text colors are not explicity set and XUL error pages. Default value is #000000.
Note: In Firefox, this can be changed via "Tools → Options → Content / Fonts & Colors → Colors... → Text and Background → Text" (Firefox 1.5 and above).
browser. display. normal_lineheight_calc_control Integer Determine method of calculating line-height (leading) in layout
-1: Uninitialized
0: Don't include external leading
1: Use what the font vendor provides
2 (default): Compensate leading if vendor's leading is insufficient
browser. display. screen_resolution Integer Firefox 1.5 only DPI of display device. Affects CSS absolute length units (e.g. pt, mm).
-1 (default): Use the operating system's logical resolution or 96 DPI, whichever is greater
0: Force use of operating system's logical resolution
(n): Assume screen DPI of n. Default DPI is 96.
Note: In Firefox, this can be changed via "Tools → Options → Content → Advanced → Display Resolution". See browser. screen_resolution for Firefox 1.0.x or layout. css. dpi for Firefox 2.0+.
browser. display. show_image_placeholders Boolean True (default): Show placeholders while image is loading
False: Opposite of above
browser. display. use_document_colors Boolean True (default): Allow documents to specify colors to use
False: Opposite of above
Note: In Firefox, this can be changed via "Tools → Options → Content / Fonts & Colors → Colors → Allow pages to chose their own colors, instead of my selections above" (Firefox 1.5 and above).
browser. display. use_document_fonts Integer 0: Never use document's fonts
1: Allow documents to specify fonts to use
2: Always use document's fonts (deprecated)
Note: In Firefox, this can be changed (between 0 and 1) via "Tools → Options → Content / Fonts & Colors → Advanced → Allow pages to chose their own fonts, instead of my selections above" (Firefox 1.5 and above).
In SeaMonkey, the corresponding setting is Edit → Preferences → Appearance → Fonts → [√] Allow documents to use other fonts
browser. display. use_focus_colors Boolean True: Set colors on focused items according to preferences
False (default): Do not set colors on focused items
browser. display. use_system_colors Boolean True: Use colors specified by OS to display documents
False (default): Opposite of above
Note: In Firefox, this can be changed via "Tools → Options → Content / Fonts & Colors → Colors → Use system colors" (Firefox 1.5 and above).
browser. dom. document. all. disabled Boolean True: Disables emulation of IE's document.all collection
False (default): Enable undetectable document.all support in quirks mode (see bug 248549)
browser. dom. global_scope_pollution. disabled Boolean True: Disable the more aggressive emulation of IE's "IDs directly accessible in the global scope" behavior.
False (default): Automatically add IDs to the global (window) scope in quirks mode.
browser. dom. window. dump. enabled Boolean True: Enable JavaScript dump() output
False: Opposite of the above
browser. download. defaultFolder String Holds the path of the default download directory determined from browser.download.folderList. Not set by default; set after the user configures their download options.
browser. download. dir String The last directory used for saving a file from the "What should (browser) do with this file?" dialog.
browser. download. downloadDir String Determines the directory to download to when browser.download.useDownloadDir is false. Appears to mirror browser.download.dir.
browser. download. folderList Integer Which of several internally-specified locations to use for the default download directory
0: the desktop
1 (default): the downloads folder
2: the last folder specified for a download
Note: In Firefox, this can be changed via "Tools → Options → Main / Downloads → Save files to... (Firefox 2 and above) or Downloads/Download Folder → Save all files to this folder" (Firefox 1.5).
browser. download. hide_plugins_without_extensions Boolean True (default): In the Download Actions dialog, remove entries where no file extensions are associated with a plugin.
False: Opposite of the above.
browser. download. lastDir String Path to the last directory used for a download via "Save As."
browser. download. manager. alertOnEXEOpen Boolean True (default): warn the user attempting to open an executable from the Download Manager
False: display no warning and allow executable to be run
Note: In Firefox, this can be changed by checking the "Don't ask me this again" box when you encounter the alert.
browser. download. manager. closeWhenDone Boolean True: Close the Download Manager when all downloads are complete
False (default): Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Main / Downloads → Close it when all downloads are finished" (Firefox 2 and above) or Downloads / Download Manager → Close the Download Manager when all downloads are complete" (Firefox 1.5).
browser. download. manager. flashCount Integer Number of times to flash the Download Manager's taskbar entry when the DM is not in the foreground. Set to 0 to disable flashing. Default value is 2.
browser. download. manager. focusWhenStarting Boolean True: Set the Download Manager window as active when starting a download
False (default): Leave the window in the background when starting a download
browser. download. manager. openDelay Integer If a download takes less than this number of milliseconds to complete, do not open the Download Manager window. Default value is 0 (always show Download Manager window).
browser. download. manager. retention Integer When to remove downloaded files' entries from the Download Manager
0: Upon successful download
1: When the browser exits
2 (default): Manually
Note: In Firefox, this can be changed via "Tools → Options → Privacy / History → Remember what I've downloaded" (Firefox 2 and above) or "Privacy → Download History → Remove files from the Download Manager" (Firefox 1.5).
browser. download. manager. showAlertInterval Integer Number of milliseconds after downloads complete to show the "completed" alert. Default value is 2000.
browser. download. manager. showAlertOnComplete Boolean True (default): popup window at bottom right corner of the screen will appear once all downloads are finished.
False: the popup window will not appear.
browser. download. manager. scanWhenDone Boolean True (default): Scan files for viruses when they finish downloading
False: Do not scan downloads for viruses
browser. download. manager. showWhenStarting Boolean True (default): Show Download Manager window when a download begins
False: Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Main / Downloads → Show the Downloads window when downloading a file" (Firefox 2 and above) or "Tools → Options → Downloads / Download Manager → Show Download Manager when a download begins" (Firefox 1.5)
browser. download. manager. skipWinSecurityPolicyChecks Boolean True: Bypass the Windows security check (ignore system security settings for executable file downloads).

False: (default) Use Windows' security setting for executable file downloads ("Launching applications and unsafe files" setting in Internet Options). This blocks executable file downloads if the Windows setting is set to "Disable".
Note: Added in bug 445158 for Firefox 3 (3.0.6, 3.1b2 and above). No longer used in Firefox 3.6 and above (removed in bug 504804).

browser. download. manager. useWindow Boolean True: Use the Download Manager window for downloads
False: Opposite of the above
Note: In Firefox, this is effectively the same as setting browser.download.manager.showWhenStarting to false; the Download Manager is used for downloads regardless of the setting.
Note: This was removed in bug 439495 for Firefox 3.1.
browser. download. save_converter_index Integer The format to save web pages in
0: Web Page (Complete)
1: Web Page (HTML Only)
2: Text
Note: In Firefox, this setting is remembered from the option you choose in the Save As dialog.
browser. download. show_plugins_in_list Boolean True (default): In the Download Actions dialog, display actions and filetypes associated with installed plugins.
False: Opposite of the above.
browser. download. useDownloadDir Boolean True (default): Without asking a location, download files to the directory specified in browser.download.folderList
False: Ask where to save every file
Note: In Firefox, this can be changed via "Tools → Options → Main / Downloads → Always ask me where to save files (Firefox 2 and above) or Downloads / Download Folder → Ask me where to save every file" (Firefox 1.5)
browser. enable_automatic_image_resizing Boolean True (default): When viewing an image not in a web page, the image will be resized to fit in the browser window if it is too large for the browser window. The image can be shown in its real size by left clicking on it.
False: Images are always shown in their real size.
Note: In Firefox, this can be changed via "Tools → Options → Advanced → General → Resize large images to fit in the browser window (Firefox 1.0.x and 1.5)". UI removed in Firefox 2.0+.
browser. feedview. articleLength Integer Pref removed. Previously:
The number of words per feed item to display. Default value is 50.
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. reloadInterval Integer Pref removed. Previously:
Determines how often in seconds to reload the currently rendered feed. Default value is 0 (never reload).
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. showBar Boolean Pref removed. Previously:
True (default): Display the options settings in feed view.
False: Opposite of the above
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. showImage Boolean Pref removed. Previously:
True (default): Display images embedded in feed items in-line.
False: Opposite of the above.
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. showMenu Boolean Pref removed. Previously:
True (default): Display a menu alongside rendered feeds with relevant functions
False: Opposite of the above.
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. timerInterval Integer Pref removed. Previously:
Determines how often to refresh the feed. Default value is 0 (no refresh).
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. externalCSS String Pref removed. Previously:
Path to a custom CSS file to apply to feeds. Default value is an empty string.
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. fixup. alternate. enabled Boolean True (default): Try to fix up http://foo to http://(prefix)foo(suffix)
False: Do not second-guess the user
browser. fixup. alternate. prefix String The prefix to prepend when attempting to fix an entered URL. Default is "www." (includes full stop). Requires browser.fixup.alternate.enabled be true.
browser. fixup. alternate. suffix String The suffix to append when attempting to fix an entered URL. Default is ".com". Requires browser.fixup.alternate.enabled be true.
browser. fixup. hide_user_pass Boolean True (default): When attempting to fix an entered URL, do not fix an entered password along with it (i.e. do not turn http://user:password@foo into http://user:password@(prefix)foo(suffix) but instead http://user@(prefix)foo(suffix))
False: Include entered password in fixed URL
browser. fixup. use-utf8 Boolean Firefox 11 / SeaMonkey 2.8 and above only. See bug 647403.
Default: false (but true on zh-TW localized builds).
browser. formfill. enable Boolean True (default): Save information entered in web page forms and the Search Bar
False: Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Privacy / History → Remember what I enter in forms and the search bar" (Firefox 2 and above) or "Tools → Options → Privacy → Saved Forms → Save information I enter in forms and the Search Bar" (Firefox 1.5)
browser. forms. submit. backwards_compatible Boolean True (default): Leave off mandatory Content-Transfer-Encoding header when submitting HTML forms
False: Send header as the spec requires
Note: Sending the header "used to cause Bad Things, including server crashes" according to comments in the Mozilla source (see bug 83065). Eventually this pref may disappear.
browser. frames. enabled Boolean True (default): Enables the display of HTML frames
False: Opposite of the above; displays <noframes> content instead
browser. fullscreen. animateUp Integer Controls toolbar and tab strip animation while in Full Screen.
0: No toolbar and tab strip animation
1 (default): Animates only first collapse.
2: Animates each collapse.
browser. fullscreen. autohide Boolean Hides toolbar and tab strip when entering Full Screen.
True (default): Shows toolbar and tab strip.
False: Hides toolbar and tab strip
browser. goBrowsing. enabled Boolean True (default): If a normal DNS lookup times out, try hitting Google
False: Opposite of the above
Note: No longer used
browser. helperApps. alwaysAsk. force Boolean True: Always ask what to do with an unknown MIME type, and disable option to remember what to open it with
False (default): Opposite of above
browser. helperApps. deleteTempFileOnExit Boolean True: Delete temporary files on exit. See comment 19 on bug 238789 (especially Mac)
False (same as default unset): Opposite of above (keep the files)
browser. helperApps. neverAsk. openFile String A comma-separated list of MIME types to open directly without asking for confirmation. Default value is an empty string.
browser. helperApps. neverAsk. saveToDisk String A comma-separated list of MIME types to save to disk without asking what to use to open the file. Default value is an empty string.
browser. hiddenWindowChromeURL String The chrome:// URL for the hidden window. Used in Mac OS X for when the browser is running but has no windows open. Default value is chrome://browser/content/hiddenWindow.xul
browser. history. grouping String How to group entries in the history window (not applicable for Firefox's History sidebar). Default value is day.
browser. history_expire_days Integer Number of maximum days to remember visited pages in history. Default value is 9 for SeaMonkey and Firefox 2, 180 for Firefox 3.
Note: In Firefox 2, this can be changed via "Tools → Options → Privacy → History → Remember visited pages for the last ___ days". No UI for Firefox 3.
browser. history_expire_days_min Integer Number of minimum days to remember visited pages in history. Default value is 90.
Note: In Firefox 3, this can be changed via “Keep my history for at least ___ days” under “Tools → Options → Privacy → History”
browser. history_expire_sites Integer Maximum number of websites to keep in history. Default value is 40000.
browser. jsannoyances. disabled Boolean The collective state of several other preferences; namely, dom.event.contextmenu.enabled, dom.disable_window_move_resize, dom.disable_window_flip, dom.disable_window_open_feature.status, and dom.disable_window_status_change. Used by the preferences dialog for tracking; changing the value of this preference manually does not change the tracked preferences.
True: Consider all of the above preferences to be true (except dom.event.contextmenu.enabled, which is considered to be false)
False (default): Opposite of the above
Note: Firefox 1.5 and above only.
browser. link. open_external Integer Where to open links sent to the browser from an external application
2 (default in SeaMonkey): Opens external links in a new window
3 (default in Firefox): Opens external links in a new tab in the most recent window
1 (or anything else): Opens external links in current window
Note: In Firefox 1.5, this can be changed via "Tools → Options → Tabs → Open links from other applications in:"; in Firefox 2 and above, via “Tools → Options → Tabs → New pages should be opened in:” (same as browser.link. open_newwindow) and in SeaMonkey, via "Edit -> Preferences -> Navigator -> Tabbed browsing / Links from other applications -> Open links passed from another applications in".

Pref removed from Firefox 3.5

browser. link. open_newwindow Integer Where to open links that would normally open in a new window
2 (default in SeaMonkey and Firefox 1.5): In a new window
3 (default in Firefox 2 and above): In a new tab
1 (or anything else): In the current tab or window
Note: In Firefox 1.5, this can be changed via "Tools → Options → Tabs → Force links that open new windows to open in:"; in Firefox 2 and above, via “Tools → Options → Tabs → New pages should be opened in:” (same as browser.link.open_external) and, in SeaMonkey, via "Edit -> Preferences -> Navigator -> Tabbed browsing / Link open behavior -> Open links meant to open a new window in".
browser. link. open_newwindow. restriction Integer Firefox and SeaMonkey only. Source: The Burning Edge.
0 (Default in Firefox 1.0.x and SeaMonkey): Force all new windows opened by JavaScript into tabs.
1: Let all windows opened by JavaScript open in new windows. (Default behavior in IE.)
2 (Default in Firefox 1.5 and above): Catch new windows opened by JavaScript that do not have specific values set (how large the window should be, whether it should have a status bar, etc.) This is useful because some popups are legitimate — it really is useful to be able to see both the popup and the original window at the same time. However, most advertising popups also open in new windows with values set, so beware.
browser. link. open_newwindow. ui Integer Determine which new window open options are available from the UI. No longer used in Firefox 1.0. Default value is 3.
browser. microsummary. enabled Boolean True (default): Allow the microsummary service to retrieve information for bookmarks with microsummaries.
False: Prevent microsummary updates to bookmarks.
browser. microsummary. generatorUpdateInterval Integer Determines how often to check for updates to microsummary generators when generator updates are enabled. A non-negative integer, in seconds, determining the amount of time between microsummary generator update checks. If unspecified, updates occur weekly (7 * 86400 seconds apart).
browser. microsummary. requestTimeout Integer Determines how long to wait for a response until the connection is cancelled. A positive integer determining the number of seconds to wait until cancelling microsummary loads that take too long. Default value is 300.
browser. microsummary. updateGenerators Boolean True (default): Periodically check for updates to microsummary generators.
False: Do not update microsummary generators.
browser. microsummary. updateInterval Integer Determines how often microsummaries’ target pages are re-fetched for new information. Number of minutes between microsummary updates for microsummaries that do not specify an update interval. Default is 30.
browser. offline Boolean Status of the "Work Offline" option
True: Attempt to retrieve pages from cache. Do not make external connections to retrieve resources.
False (default): Assume a connection is present and retrieve resources where necessary.
Note: In Firefox, this can be changed via "File → Work Offline"
browser. places. createdDefaultQueries Boolean True: A "Most Viewed" folder in the Bookmarks Toolbar Folder has been created already; do not create a new one.
False (default): Create a "Most Viewed" folder in the Bookmarks Toolbar Folder, then toggle this preference to True.
browser. popups. showPopupBlocker Boolean True (default): Show an icon in the status bar when a popup has been blocked.
False: Do not show an icon in the status bar when a popup has been blocked.
browser. preferences. advanced. selectedTabIndex Integer Determines which tab in the Advanced section of the preferences is visible.
0 (default): General
1: Update
2: Security
browser. preferences. animateFadeIn Boolean True (default in Mac OS X): When switching prefs panels, change the height of the window and fade the new panel in over about a second.
False (default everywhere else): Do not animate switching pref panels
Note: Firefox 1.5 and above only.
browser. preferences. instantApply Boolean True (default in all platforms but Windows): Changes to preferences are active immediately. The preferences window is not modal. Instead of "OK" and "Cancel" buttons, there is only a "Close" button.
False: Changes to preferences occur after clicking "OK" button. The preference window is modal.
 
Applies to:
  • Firefox 1.5 and above
  • SeaMonkey 2 dated 20071028 and later, for preferences migrated to "new toolkit".
browser. preferences. lastpanel Integer Which part of the preferences window was displayed the last time it was closed. In Firefox:
0: General
1: Privacy
2: Web Features
3: Downloads
4: Advanced
Note: In Firefox, this is determined by the section of "Tools → Options" you are viewing when you close the dialog.
browser. preferences. privacy. selectedTabIndex Integer Determines which tab in the Privacy section of the preferences is visible.
0 (default): History
1: Saved Forms
2: Passwords
3: Download History
4: Cookies
5: Cache
browser. related. autoload Integer Automatically load "What's Related" for a given URL
0: Always
1 (default): After first use (default)
2: Never
Note: This is not used in Firefox (there is no "What's Related").
browser. related. disabledForDomains String A comma-separated list of domains for which "What's Related" is disabled. Default value is an empty string.
Note: This is not used in Firefox (there is no "What's Related").
browser. related. enabled Boolean Setting for "What's Related"
True (default): Enable
False: Disable
Note: This is not used in Firefox (there is no "What's Related").
browser. related. provider String The URL to retrieve "What's Related" data from. Default value is http://www-rl.netscape.com/wtgn?
Note: This is not used in Firefox (there is no "What's Related").
browser. safebrowsing. dataProvider Integer The provider ID of the site used to get the web forgery list. Default value is 0.
Note: This references the pref tree browser.safebrowsing.provider.*
browser. safebrowsing. enabled Boolean Whether to determine if a site is a web forgery or not.
True (default): Check visited sites
False: Do not check any sites
Note: This can be changed in Firefox via "Tools → Options → Security / Tell me if the site I'm visiting is a suspected forgery".
browser. safebrowsing. provider. * Tree Tree containing provider information used in the safe browsing process.
Note: There is currently only one default provider (Google); however, more may be added.
browser. safebrowsing. remoteLookups Boolean Method to determine if a site is a web forgery.
True: Ask provider by sending a request
False (default): Use internal list
Note: This can be changed in Firefox via "Tools → Options → Security" radio buttons:
* "Check using a downloaded list of suspected sites" (False)
* "Check by asking ____ about each site I visit" (True).
Note: When an internal list is used, it is updated about once an hour from the provider.
browser. safebrowsing. warning.infoURL String The FAQ URL for the Safe Browsing feature.
browser. screen_resolution Integer Firefox 1.0.x only DPI of display device. Affects CSS absolute length units (e.g. pt, mm).
-1 (default): Use the operating system's logical resolution or 96 DPI, whichever is greater
0: Force use of operating system's logical resolution
(n): Assume screen DPI of n. Default DPI is 96.
Note: In Firefox 1.0.x, this can be changed via "Tools → Options → General → Fonts & Colors → Display Resolution". See browser. display. screen_resolution for Firefox 1.5.0.x or layout. css. dpi for Firefox 2.0+.
browser. search. basic. min_ver String Version number used to determine which search engine plugins should be installed/displayed. Default value is 0.0.
browser. search. defaultenginename String Default search engine plugin to use. Default value is Google.
browser. search. defaulturl String URL to prepend to search terms. Default value is http://www.google.com/search?lr=&ie=UTF-8&oe=UTF-8&q=
browser. search. log Boolean True: Log debugging information about the search service to the JavaScript Console and stdout.
False (default): Do not log debugging information.
Note: Firefox 2.0 and above only.
browser. search. openintab Boolean True: When performing a search from the Search Bar, open the results in a new tab.
False (default): Open search results in the current tab/window.
Note: Firefox nightly trunk builds only.
browser. search. order. (digit) String (digit) is used to weight the search engine specified by the value for sorting in the list of search engines.
browser. search. order. (name) (. digit) String Used for weighting search engine entry sorting. Points to .properties file.
browser. search. param. (name). (digit). ("custom" or "default") String Used for adding arbitrary variables to the search query of the (name) search plugin.
browser. search. selectedEngine String Name of currently selected search engine plugin
browser. search. selectedEngineInDialog String Name of currently selected search engine plugin in the search dialog (used when the Search Bar is hidden)
Note: Firefox 1.5 and above only.
browser. search. update Boolean True (default): Automatically check for updates to search plugins.
False: Opposite of the above.
Note: Firefox 1.5 and above only.
browser. sessionhistory. cache_subframes Boolean True: Cache the content viewer (when browser.sessionhistory.max_total_viewers is greater than 0) for subframes
False (default): Opposite of the above
Note: Firefox 1.5 and above only.
browser. sessionhistory. max_entries Integer The maximum number of pages in the browser's session history, i.e. the maximum number of URLs you can traverse purely through the Back/Forward buttons. Default value is 50.
browser. sessionhistory. max_total_viewers Integer Determines the maximum number of content viewers to cache for "bfcache" (fast back/forward navigation). Default value is -1 (calculate based on available memory). All values less than 0 are equivalent.
Note: Firefox 1.5 and above only. Supersedes browser.sessionhistory.max_viewers.
browser. sessionhistory. max_viewers Integer The number of content viewers to cache for "bfcache" (fast back/forward navigation). Default value is 3.
Note: Deer Park/Firefox 1.5b1 only. Functionality has been replaced by browser.sessionhistory.max_total_viewers.
browser. sessionstore. max_concurrent_tabs Integer  ?
Firefox 4.0b7 and above
See http://twitter.com/limi/status/2489319692435456
browser. shell. checkDefaultBrowser Boolean Check the system default browser on startup.
True (default): Check to see if the browser is set as default; if not, ask if the user wants it set that way
False: Do not perform the check
Note: In Firefox, this can be changed via "Tools → Options → Main / System Defaults" (Firefox 2.0 and above) or "Tools → Options → General → Default Browser" (Firefox 1.5 and 1.0.x).
browser. startup. homepage String URL of homepage, or pipe (|)-separated list of URLs to open in tabs when going to the homepage
In SeaMonkey (or at least in SeaMonkey 2 and above), this is the URL of your first or only homepage tab. If you have a multitab homepage, additional URLs are in browser.startup.homepage.1, browser.startup.homepage.2, etc.
Note: This can be changed in Firefox via "Tools → Options → Main (Firefox 1.5 and 1.0.x: General) → Homepage" and in SeaMonkey via "Edit → Preferences → Browser → Home Page".
browser. startup. homepage. count Integer In SeaMonkey, the number of tabs of your multitab homepage, or 1 if you use a single-tab homepage.
browser. startup. homepage_override. 1 Boolean Stub for browser.startup.homepage_override (used in Netscape 4.x). No longer used. Default value is false.
browser. startup. homepage_override. mstone String The last browser version (milestone) this profile was loaded with. If it differs from the current version, pref is changed to current version.
browser. startup. homepage_reset String If, during installation, the user requested that their homepage be reset, get the new homepage value from this location. Default value is resource:/browserconfig.properties
browser. startup. page Integer Page to open on browser startup
0: Blank
1 (default): Home (a.k.a. browser.startup.homepage)
2: Last (works in Firefox 2 and above; experimental in the latest nightlies of SeaMonkey 2.0b1pre; probably doesn't work in earlier versions).
Note: This can be changed in Firefox via "Tools → Options → Main → Startup → When Firefox starts", and in SeaMonkey via "Edit → Preferences → Browser → Display on → Browser startup".
browser. tabs. autoHide Boolean Behavior for the tab bar when only one tab exists
True (default): Hide the tab bar
False: Always show the tab bar
Note: In Firefox, this can be changed via "Tools → Options → Tabs → Always show the tab bar" (Firefox 2 and above) or Tools → Options → Tabs → Hide the tab bar when only one web site is open (Firefox 1.5).
browser. tabs. closeButtons Integer (Firefox 2.0 and above) This preference controls how close buttons can be displayed on tabs.
0: Display a close button on the active tab only
1: (default) Display a close button on each tab
2: Don't display any close buttons
3: Display a single close button at the end of the tab bar (Firefox 1.x behavior)
browser. tabs. closeWindowWithLastTab Boolean (Firefox 3.5 and above) This preference controls whether closing the last tab, closes the window.
True: Close window when closing last tab (default)
False: Do not close the window when closing last tab (pre Firefox 3.5 behavior)
Note: Changing to False prevents Firefox from closing the window when you close the last tab such as with Ctrl+W, and subsequently from closing Firefox itself when closing the last tab of the last Firefox window.
browser. tabs. forceHide Boolean Display of the tab bar
True: Hide the tab bar
False: Show tab bar normally
Note: This is not used to enable/disable the tab bar. It's used internally to decide whether or not to show the tabbed bar.
browser. tabs. insertRelatedAfterCurrent Boolean (Firefox 3.6 and above) This preference controls where new tabs will be located.
True (default): Open new tabs to the right of the parent tab.
False: Restores pre Firefox 3.6 behavior where new tabs are opened at the far right of the tabs bar.
Note: Bug 465673 -- tabs opened from links should appear next to the current tab (instead of at the end of the tabstrip)
browser. tabs. loadBookmarksInBackground Boolean Focus behavior of new tabs from bookmarks & history
True: When you open a bookmark in a new tab then that tab will load in the background without taking focus from the current tab.
False (default): When you open a bookmark in a new tab then that tab will become the current tab.
Note: you likely want to set this to the same setting value as used in browser.tabs.loadInBackground (Bug 469456)
Note: Firefox 1.0.x had a Tabs option for "Select New Tabs from Bookmarks or History"
browser. tabs. loadDivertedInBackground Boolean Determines behavior of pages normally meant to open in a new window (such as target="_blank" or from an external program), but that have instead been loaded in a new tab.
True: Load the new tab in the background, leaving focus on the current tab
False (default): Load the new tab in the foreground, taking the focus from the current tab.
Note: Setting this preference to True will still bring the browser to the front when opening links from outside the browser.

Note: target="_new" creates/reuses a window named "_new" and is frequently used by Google.   target="_blank" loads the designated document in a new, unnamed window [ [1]].

browser. tabs. loadFolderAndReplace Boolean True (default): When opening a folder of bookmarks in tabs, the existing tabs will be replaced by the new bookmark pages.
False: Existing tabs will be preserved when loading a folder of bookmarks. The bookmark pages will be loaded in tabs that are appended to the current tabs.
Note: This option was removed in Firefox 3 alpha 8.
browser. tabs. loadGroup Integer 0: Append group to current tab set
1 (default): Replace current tab set with group
Note: Mozilla Suite/SeaMonkey only.
browser. tabs. loadInBackground Boolean Focus behavior for new tabs from links
True (default): Do not focus new tabs opened from links (load in background)
False: Opposite of above
Note: bookmarks & history can be opened similarly with browser.tabs.loadBookmarksInBackground
Note: In Firefox, this can be changed via "Tools → Options → Tabs → When I open a link in a new tab, switch to it immediately" (Firefox 2 and above) or "Tools → Options → Tabs → Select new tabs opened from links" (Firefox 1.5).
browser. tabs. loadOnNewTab Integer Determines what will be displayed in a new tab
-1: Browser startup page
0 (default): Blank page
1: Homepage
2: Last visited page
Note: Does not work in Firefox (see bug 269664).
browser. tabs. onTop Boolean (Firefox 4.0 and above) Determines position of the Tabs Bar relative to the Location Bar.
True (default): Tabs Bar above Location Bar
False: Restores old behavior of Tabs Bar below Location Bar
Note: bug 755593 will soon remove tabs-on-bottom mode. Once it is RESOLVED FIXED, this pref will no longer be effective.
browser. tabs. opentabfor. bookmarks Boolean Controls if a clicked bookmark will open in a new tab when middleclicked.
Note: Pref removed (obsolete). Functionality proposed as enhancement request.
browser. tabs. opentabfor. middleclick Boolean Determines the behavior of a link when middle-clicked.
True (default): Opens link in new tab
False: Opens link in new window
browser. tabs. opentabfor. searchdialog Boolean Determines whether to create a new tab for the search results from queries entered in the search dialog (used when the Search Bar is hidden)
Note: Firefox 1.5 and above only.
browser. tabs. opentabfor. urlbar Boolean Pref removed (unused). Previously:
Determines the behavior of pressing Enter in the address bar or clicking the Go button.
True (default): Open URL in new tab
False: Open URL in current tab
Note: Functionality proposed as enhancement request.
browser. tabs. opentabfor. windowopen Boolean Pref removed (obsolete).
browser. tabs. showSingleWindowModePrefs Boolean Determines whether to display "Single Window Mode" settings in preferences in Firefox 1.0.x (see bug 266759). Note: Preference is obsolete and has no effect in Firefox 1.5 and above
True: Show "Force links that open in new windows to open in..." options under "Tools → Options → Advanced → Tabbed Browsing" (Firefox 1.0.x)
False (default): Opposite of above
browser. tabs. warnOnClose Boolean True (default): The browser will prompt for confirmation when closing the browser when more than one tab is open.
False: No warnings will be given when closing the browser with more than one tab.
Note: In Firefox, this can be changed via "Tools → Options → Tabs → Warn (me) when closing multiple tabs" (Firefox 1.5 and above).
browser. tabs. warnOnCloseOther Boolean True (default): The browser will prompt for confirmation when closing all other tabs from the tab context menu ("Close Other Tabs")
False: Opposite of the above
browser. throbber. url String Indicates what URL to load when the throbber is clicked. Default value is http://www.mozilla.org/products/firefox/central.html
browser. trim_user_and_password Boolean Unused
browser. triple_click_selects_paragraph Boolean True (default): Select the entire paragraph under the mouse cursor when triple-clicking.
False: Select the line under the mouse cursor when triple-clicking
Note: This feature is currently only stable on trunk (1.9).
browser. turbo. enabled Boolean Pref removed (obsolete). Previously:
Determined whether to load browser in "Turbo Mode" (aka "quick launch") (Windows/Mozilla Suite only)
True: Load some Mozilla code into memory on Windows boot
False (default): Load browser normally on program execution
browser. underline_anchors Boolean Determines default text-decoration of anchor elements.
True (default): Underlines links
False: Opposite of above
Note: In Firefox, this can be changed via "Tools → Options → Content → Fonts & Colors → Underline links"
browser. update. resetHomepage Boolean Determine whether to reset homepage during browser installation
True: Reset homepage in browser.startup.homepage to value in browser.startup.homepage_reset
False (default): Do not reset homepage
browser. urlbar. autoFill Boolean True: Enables inline autocomplete.
False (default): Opposite of above.
browser. urlbar. autocomplete. enabled Boolean True (default)
False
browser. urlbar. clickAtEndSelects Boolean True (default)
False
browser. urlbar. clickSelectsAll Boolean True (default in non-Unix builds): Select the contents of the address bar when it is clicked
False (default everywhere else): Opposite of above
browser. urlbar. default. behavior Integer Customizes the search behavior of the location bar, starting in Firefox 3.5 and SeaMonkey 2. See the linked article for values and UI.
browser. urlbar. doubleClickSelectsAll Boolean True: Select the contents of the address bar when it is double clicked
False(default): Opposite of above
browser. urlbar. filter. javascript Boolean True (default): Filter out “javascript:” URLs from appearing in the Location Bar autocomplete dropdown.
False: Allow “javascript:” URLs to appear in the dropdown.
browser. urlbar. formatting. enabled Boolean True (default): Format url in location bar to emphasize domain name.
False: Don't fade non domain portions of url in location bar.
browser. urlbar. match. title String See Location Bar search
browser. urlbar. match. url String See Location Bar search
browser. urlbar. matchBehavior Integer Determines how to use word boundaries when searching for items in the Location Bar.
0 Search anywhere within available text, irrespective of word boundaries.
1 (default): Use word boundaries first when searching, then try matching anywhere
2: Use only word boundaries when searching for typed text
3: Match only the beginning of page URLs and titles
browser. urlbar. matchOnlyTyped Boolean Determines behavior of autocomplete in Location Bar. No longer used in Firefox 3.5 - replaced by browser.urlbar.default.behavior (see bugs 463483 and 463558)
True: Only matches typing against URLs specifically typed into Location Bar
False (default): Match against history
browser. urlbar. matchOnWordBoundary Boolean Determines behavior of autocomplete in Location Bar
True (default): Use word boundaries when searching for typed text in the Location Bar autocomplete.
False: Search anywhere within available text, irrespective of word boundaries.
Obsoleted by browser. urlbar. matchBehavior.
browser. urlbar. maxRichResults Integer Determines how many entries should appear (at most) in the dropdown in Location Bar.
browser. urlbar. restrict. bookmark String See Location Bar search
browser. urlbar. restrict. history String See Location Bar search
browser. urlbar. restrict. tag String See Location Bar search
browser. urlbar. restrict. typed String See Location Bar search
browser. urlbar. search. chunkSize Integer Number of dropdowns to fetch at a time. Default is 1000.
browser. urlbar. search. timeout Integer Number of milliseconds to wait between fetching batches of dropdown items. Default is 100 (1/10th of a second).
browser. urlbar. showPopup Boolean True (default)
False
browser. urlbar. showSearch Boolean True (default)
False
browser. urlbar. trimURLs Boolean True (default): Trim "http://" prefix from url address displayed in location bar .
False: Don't trim url in location bar.
browser. visited_color String The default color for visited links as a hex code. Default is #551A8B
Note: In Firefox, this can be changed via "Tools → Options → Content → Fonts & Colors → Visited Links"
browser. windows. loadOnNewWindow Integer Set what should be displayed in a newly created window
-1: Browser Startup Page
0: Blank Page
1 (default): Your Homepage
2: Last Visited
browser. xul. error_pages. enabled Boolean True (default in Firefox 1.5 and above and SeaMonkey): The browser will use error pages.
False (default in Firefox 1.0.x and below): The browser will use error alert boxes.
browser. zoom. full Boolean True (Default): Full page zoom
False: Text zoom
browser. zoom. siteSpecific Boolean True (Default): Remember the zoom level on a per-site basis.
False: The zoom level should be applied on the current tab only.

Config.

Name Type Meaning of Values
config. trim_on_minimize Boolean Windows-only. Determines how Windows handles memory for the browser when minimizing. Setting to False will often prevent delays when restoring the window (see bug 76831).
True: Allow Windows to trim the working set when the browser is minimized
False (default): Prevent Windows from trimming the working set
config. use_system_prefs Boolean True: Use preferences set by operating system (e.g. proxies, accessibility)
False (default): Opposite of the above
Note: Seems to be unused in Firefox 1.0
config. use_system_prefs. accessibility Boolean True: The system is configured with accessibility features; use them
False (default): Opposite of the above
Note: Seems to be unused in Firefox 1.0

Content.

content.* allows you to configure the frequency of certain events when parsing and rendering web pages.

content.* has been migrated to Category:Preferences.

DOM.

Name Type Meaning of Values
dom. allow_scripts_to_close_windows Boolean Determines which close() operations are legal.
True: Any script may close any window
False (default): Only windows opened via script may be closed via close().
dom. disable_image_src_set Boolean Determines whether scripts may change the .src member of image objects (effectively, whether images can be changed via JavaScript)
True: Scripts may not modify .src of images
False (default): Opposite of above
Note: In Mozilla Suite, this can be changed via "Edit → Preferences → Advanced → Scripts & Plug-ins → Allow scripts to: Change images" and, in Firefox 1.0.x, via "Tools → Options → Web Features → Enable JavaScript / Advanced → Allow scripts to: Change images". This option has been removed from the UI in Firefox 1.5 [2]
dom. disable_open_click_delay Integer If a popup will be created as the result of a setTimeout() or setInterval() JavaScript call and the delay specified is smaller than this value (in milliseconds), handle the popup according to the current popup blocker settings. Default value is 1000.
dom. disable_open_during_load Boolean Determines popup blocker behavior
True (default in Firefox): Block popup windows created while the page is loading
False (default in Mozilla Suite): Allow popup windows
Note: In Firefox, this can be changed via "Tools → Options → Content (Web Features in Firefox 1.0.x) → Block Popup Windows" and, in Mozilla Suite, via "Edit → Preferences → Privacy & Security → Popup Windows → Block unrequested popup windows.
dom. disable_window_flip Boolean Determines whether windows can be focus()ed via non-chrome JavaScript.
True (default in Mozilla Suite): Windows may not be set as active via JavaScript
False (default in Firefox): Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Content (Web Features in Firefox 1.0.x) → Enable JavaScript / Advanced → Allow scripts to: Raise or lower windows" and, in Mozilla Suite, via "Edit → Preferences → Advanced → Scripts & Plug-ins → Allow scripts to: Raise or lower windows".
dom. disable_window_move_resize Boolean Determines whether windows can be moved or resized via non-chrome JavaScript.
True (default in Mozilla Suite): Windows may not be moved or resized via JavaScript
False (default in Firefox): Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Content (Web Features in Firefox 1.0.x) → Enable JavaScript / Advanced → Allow scripts to: Move or resize existing windows" and, in Mozilla Suite, via "Edit → Preferences → Advanced → Scripts & Plug-ins → Allow scripts to: Move or resize existing windows".
dom. disable_window_open_feature. * Boolean Webpage authors can disable many features of a popup window that they open. Setting these preferences to true will override the author's settings and ensure that that feature is enabled and present in any popup window.
close: Prevents the close button from being disabled.
directories: Prevents the bookmarks toolbar from being hidden.
location: Prevents the address bar from being hidden
menubar: Prevents the menubar from being hidden.
minimizable: Prevents popup window minimization from being disabled.
personalbar: Prevents the bookmarks toolbar from being hidden.
resizable: Prevents popup window resizing from being disabled.
scrollbars: Prevents the scrollbars on a popup from being disabled.
status: Prevents the status bar from being hidden.
titlebar: Prevents the title bar from being hidden.
toolbar: Prevents the navigation toolbar from being hidden.
dom. disable_window_status_change Boolean Determines whether the text in the browser status bar may be set by non-chrome JavaScript.
True (default in Firefox): JavaScript access to window.status is disabled
False (default in Mozilla Suite): Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Content (Web Features in Firefox 1.0.x) → Enable JavaScript / Advanced → Allow scripts to: Change status bar text" and, in Mozilla Suite, via "Edit → Preferences → Advanced → Scripts & Plug-ins → Allow scripts to: Change status bar text".
dom. event. contextmenu. enabled Boolean Determines whether the oncontextmenu event can be caught by non-chrome JavaScript (e.g., in an anti-right-click script).
True (default): the opposite of below.
False: Webpages will not be able to affect the context menu event, thus allowing to access the context menu all the time.
Note: In Firefox, this can be changed via "Tools → Options → Content (Web Features in Firefox 1.0.x) → Advanced → Allow scripts to: Disable or replace context menus" and, in Mozilla Suite, via "Edit → Preferences → Advanced → Scripts & Plug-ins → Allow scripts to: Disable or replace context menus".
dom. ipc. plugins. enabled Boolean Determines whether plugins will run in a separate "plugin-container" process. See Plugin-container and out-of-process plugins for details. Can be overridden for plugins specified by filename (bug 539063).
True (default in Firefox 4 on Windows and Linux): Run plugins out-of-process, except for "blacklisted" plugins set in dom.ipc.plugins.enabled.<filename> with value false (see below).
False (default in Firefox 3.6.x on Windows and Linux, and in Firefox 4 on Mac OS): Do not run plugins out-of-process, except for "whitelisted" plugins set in dom.ipc.plugins.enabled.<filename> with value true (see below).
Note: First shipped in Firefox 3.6.4 for Windows and Linux only, with the plugins Adobe Flash, Apple QuickTime (Windows) and Microsoft Silverlight (Windows) whitelisted by default [3]
dom. ipc. plugins. enabled. <filename> Boolean Overrides dom.ipc.plugins.enabled (see above) for plugins specified by filename (plugin filenames can be found in about:plugins and must be specified in lowercase).
True: Run the specified plugin in a separate "plugin-container" process.
False: Do not run the specified plugin out-of-process (run within the browser process).
Windows examples:
Microsoft Silverlight: dom.ipc.plugins.enabled.npctrl.dll
Apple QuickTime: dom.ipc.plugins.enabled.npqtplugin.dll
Adobe Flash (listed as "Shockwave Flash"): dom.ipc.plugins.enabled.npswf32.dll
NPAPI test plugin: dom.ipc.plugins.enabled.nptest.dll
Linux examples:
Adobe Flash (listed as "Shockwave Flash"): dom.ipc.plugins.enabled.libflashplayer.so
NPAPI test plugin: dom.ipc.plugins.enabled.libnptest.so
Mac examples: (Firefox 4) [4]
Adobe Flash (listed as "Shockwave Flash"):dom.ipc.plugins.enabled.flash player.plugin
Java: dom.ipc.plugins.enabled.javaplugin2_npapi.plugin
dom. ipc. plugins. enabled. timeoutSecs Integer Number of seconds before an out-of-process plugin is terminated, when the browser detects that the plugin or plugin script has stopped responding. [5] Default is 45 in Firefox 3.6.6 (increased from 10). Set the value to -1 to disable plugin hang detection, so that the browser does not terminate plugins that stop responding [6] [7] [8]
Note: First shipped in Firefox 3.6.4 for Windows and Linux.
dom. max_chrome_script_run_time
and
dom. max_script_run_time
Integer Determines the maximum amount of time in seconds a script can run (with chrome or content privileges, respectively). Default values are 20 and 10 respectively. Zero or negative values mean "forever". See the details pages for former behaviour (prior to 2006-07-27).
2012-08-21: New default for chrome is 0 (forever) on SeaMonkey and Thunderbird, except on Linux, see bug 482811
dom. min_background_timeout_value Integer See the "Inactive tabs" section of the window.setTimeout method's help.
dom. popup_allowed_events String A space-separated list of the events that are allowed to create popups. Default value is "change click dblclick mouseup reset submit". A presumably complete list of events from mozilla/content/events/src/nsDOMEvent.cpp:
Form events:
select:
change:
input:
submit:
reset:

Other events:

keydown:
keypress:
keyup:
mousedown:
mouseup:
click:
dblclick:
error:
dom. popup_maximum Integer The maximum number of simultaneously open popup windows. Default value is 20.

Editor.

These settings affect libeditor (i.e. Composer and Mail). Most have no effect in Firefox.

Name Type Meaning of Values
editor. background_color Boolean Determines background color for Thunderbird editor; other forks' behaviour unknown.
#000000: Use black instead of white in editor. Works well in conjunction with .text_color, but if HTML mail is sent, it's odd to some folks.; an invert_display option would be more practical, but doesn't exist (yet).* preferences for content
#FFFFFF (default)
editor. css. default_length_unit String Determines the default units for CSS rules.
cm: centimeters
em: ems (width of the capital letter "M" in typography, but line height in CSS)
ex: ex (height of the lower-case "x")
in: inches
mm: milimeters
%: percentage of parent element
pc: picas (1/6th of an inch)
px (default): pixels
pt: points (1/72nd of an inch)
editor. htmlWrapColumn Integer The column at which HTML source wraps. Default value is 72.
editor. positioning. offset Integer The default offset, both X and Y, of absolutely positioned elements. Default value is 0.
editor. quotesPreformatted Boolean Originally meant to be a temporary preference to control the behavior of plaintext quotations inserted into email.
True: Wrap quoted email text in a pre element
False (default): Wrap quoted email text in a span element
editor. resizing. preserve_ratio Boolean Determines the behavior of resizing images in Composer.
True (default): Preserve ratio of image while resizing
False: Allow free resizing of height and width
editor. singleLine. pasteNewlines Integer Determines the behavior when pasting content containing newlines into single-line text boxes.
0 (default in Linux): Paste content intact (include newlines)
1 (default everywhere else): Paste the content only up to (but not including) the first newline
2: Replace each newline with a space
3: Remove all newlines from content
4: Substitute commas for newlines in text box
5: Remove all newlines and surrounding whitespace
editor. use_css Boolean Determines the preferred method of formatting content.
True (default): Use CSS styling where appropriate
False: Use non-CSS methods of styling content
editor. use_custom_colors Boolean Determines whether to use user-specified colors for content. No effect in Thunderbird.
True: Use colors specified in editor.* preferences for content
False (default): Use the default colors

Extensions.

This branch of preferences is usually used to hold settings for installed extensions, but there are a few that deal with extensions and themes in general.

Name Type Meaning of Values
extensions. {GUID}. description String Specify a custom description for the extension whose GUID is specified (see Localize extension descriptions for application).
extensions. autoDisableScopes Integer "Extension scopes" where newly installed addons are disabled by default (Gecko 7 and later since 2011-06-28, see bug 666437). This is an additive bit field:
1 = addons found in this profile (this bit is probably masked off)
2 = addons applying to all profiles of this user
4 = addons applying to all users of this application
8 = addons (e.g. plug-ins) applying to anyone on this computer
Default varies among versions: Undefined (no disabling, as with 0), 10 (all except app-global and user-profile), 15 (all, but does not apply to some specific locations such as IIUC installdir/extensions/ and profiledir/extensions/)
extensions. checkCompatibility Boolean Undefined (default) or True: Check extension for browser compatibility on upgrade/install.
False: Disable extension compatibility checking.
Available in Firefox and Thunderbird 2.0, SeaMonkey 2.0, Sunbird 1.0b1. Note: Use with caution (see bug 330895).
Note: In applications based on Gecko 1.9.2a and later, this preference is replaced by extensions.checkCompatibility.x.yy where x.yy should be replaced by the major and minor version numbers of the application, including the letter (a, b, pre) if present but not the 3rd and further numbers: e.g. extensions.checkCompatibility.2.1a for SeaMonkey 2.1a2pre or extensions.checkCompatibility.3.6 for Firefox 3.6.6.
extensions.checkUpdateSecurity Boolean Undefined (default) or True: Checks that extensions provide secure updates.
False: Disable secure updates checking.
Available in Firefox 3.0, Thunderbird 3.0, SeaMonkey 2.0. Note: Use with caution (see bug 378216).
extensions. disabledObsolete Boolean Indicates whether obsolete extensions have been disabled as a result of a change in the browser version.
extensions. dss. enabled Boolean True: Enable dynamic skin (theme) switching.
False (default): Require a browser restart when switching themes.
Note: Switching themes dynamically is buggy (see bug 226791).
extensions. dss. switchPending Boolean True: Non-dynamic theme switch pending a browser restart
False (default): Opposite of the above
extensions. enabledScopes Integer (Applies to Gecko 1.9.3 and later since 2010-04-07, see bug 555486)
"Scopes" from which addons will be loaded (additive bit field):
1 = addons found in this profile (cannot be disabled)
2 = addons applying to all profiles of this user
4 = addons applying to anyone using this application
8 = addons (e.g. plug-ins) applying to anyone on this computer
Default is Undefined, which means the same as 15 (addons from all scopes will be loaded unless disabled for some other reason)
See also extensions. autoDisableScopes above.
extensions. getMoreExtensionsURL String Determines the URL used for the "Get More Extensions" link in "Tools → Add-ons → Extensions" dialog.
extensions. getMoreThemesURL String Determines the URL used for the "Get More Themes" link in "Tools → Add-ons → Themes" dialog.
extensions. ignoreMTimeChanges Boolean True: Prevent extensions system from using last-modified file metadata when determining whether an extension is new (and should therefore be registered)
False (default): Opposite of the above
Note: Nightlies only.
extensions. lastAppVersion String The last version of the browser to successfully load extensions. Used to determine whether or not to disable extensions due to possible incompatibilities.
extensions. logging. enabled Boolean True: Enables some extra extension system logging (can reduce performance)
False (default): Opposite of the above
Note: Nightlies only
extensions. reporter. hidePrivacyStatement Boolean True: The user has viewed and agreed to the privacy statement for the Report Broken Website tool, so don't show it again.
False: Display the privacy statement when opening the Report Broken Website tool.
extensions. update. autoUpdate Boolean True: Automatically download and install available updates
False (default): Opposite of the above
Note: Not implemented
extensions. update. autoUpdateEnabled Boolean True (default): Allow automatic checking for updates at the specified interval
False: Opposite of the above
extensions. update. count Integer The number of extension/theme/etc. updates available. Default value is 0.
extensions. update. enabled Boolean True (default): Allow checking for updates
False: Opposite of the above
Can be overridden on a per-extension basis by setting extensions.{GUID}.update.enabled.
extensions. update. interval Integer Determines how often to check the update URL for updates.
In Firefox 1.0.x and below, default value is 604800000 (milliseconds in 1 week).
In Firefox 1.5 and above, default value is 86400 (seconds in 1 day).
extensions. update. lastUpdateDate Integer When the last extension update occurred, in UNIX epoch format (seconds since 1970-01-01). Default value is 0.
extensions. update. notifyUser Boolean A flag for whether to show the software update dialog for extensions on startup. The application sets this pref to true after it checks for extension updates in the background and finds one or more updates available. On the next startup, the dialog is shown and the pref is immediately set to false. You would not normally change this pref manually, unless debugging startup and updates. Setting it to true will cause the dialog to open on next startup, but the dialog will close immediately if there is no update pending. Unset by default (until first background check). Introduced by the patch for bug 307358.
Firefox / Thunderbird 2.x and later.
extensions. update. severity. threshold Integer The number of pending Extension/Theme updates you can have before the update notifier goes from low to medium severity. Default value is 5.
extensions. update. url String Determines the URL queried when polling for extension updates. Can be overridden on a per-extension basis by setting extensions.{GUID}.update.url. Default value is pulled from chrome://mozapps/locale/update/update.properties.

Font.

The majority of the font.* entries are of the form:

font.(font property).(font type).(language code)

The (font property) indicates that the value of the entry is one of the following:
name-list 
A comma-and-space-delimited list of font names corresponding to the (font type) and (language code) (String)
name 
A font name (String)
size 
The font size, in pixels (Integer)
The (font type) indicates which CSS generic-family is being referenced in the value, or simply whether the font is fixed-width or variable-width. The (font type) is one of the following:
serif 
(e.g. Times)
sans-serif 
(e.g. Helvetica)
cursive 
(e.g. Zapf-Chancery)
fantasy 
(e.g. Western)
monospace 
(e.g. Courier)
fixed 
Any fixed-width font
variable 
Any variable-width font
The (language code) is an ISO 639-2 value.

Other font.* entries are listed below.

Name Type Meaning of Values
font. default (. language code) String The default generic-family to use. If a language code is specified, the preference only applies to that language.
serif (default): Serif
sans-serif: Sans-serif
font. language. group String The user's language group. Pulled from the localized data at chrome://global/locale/intl.properties by default on installation.
font. size. nav4rounding Boolean Unused (obsolete). Previously:
True: In Windows, adjust rounding of some pixel font sizes to match Netscape 4.x's (incorrect) rounding
False (default): Display fonts normally
font. FreeType2.enable Boolean Attempt to use FreeType fonts.
font. FreeType2.printing Boolean Attempt to use FreeType fonts when printing using the PostScript printing system.

Geo.

Name Type Meaning of Values
geo. enabled Boolean Is location aware browsing enabled. Default is true. See http://www.mozilla.com/en-US/firefox/geolocation/
geo. wifi. url String Which geolocation service provider to use. Default is https://www.google.com/loc/json

General.

Name Type Meaning of Values
general. autoScroll Boolean Status of the autoscroll option (middle-clicking on a web page produces a scrolling icon and will automatically scroll the page based on the pointer's relative location to the icon)
True (default): Activate autoscroll
False (default in *nix): Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Advanced → General → Browsing → Use autoscrolling"
general. config. filename String A .cfg file to parse and read for AutoConfig. Unset by default.
general. config. obscure_value Integer An integer to use when obscuring the AutoConfig file saved to and read from disk. Default value is 13 (effectively, ROT-13 the content).
general. config. vendor String A vendor ID associated with the AutoConfig file.
general. skins. selectedSkin String The current skin used by the browser. Default value is classic/1.0.
Note: In Firefox, this can be changed via "Tools → Add-ons → Themes" (Firefox 2) or "Tools → Themes" (Firefox 1.5 and below)
general. smoothScroll Boolean Status of ths smooth scrolling option (scrolling on a web page moves page content pixelwise rather than line-by-line)
True: Activate smooth scrolling
False (default): Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Advanced → General → Browsing → Use smooth scrolling"
general. startup. browser Boolean True (default): When launching Mozilla Suite or SeaMonkey, load the browser component
False: Opposite of the above
Note: This preference has little to no significance in Firefox as it is only a browser. It has no effect since Firefox 1.5.
general. useragent. contentlocale String The content locale ISO 639-2 value specified in the User-Agent string
general. useragent. extra. (product name/version) String Allows an arbitrary number of strings to be added to the end of the User-Agent string. By default, general.useragent.extra.<product> is defined and set to <product>/<version>. See bug 274928 for more information.
Note: Only Firefox 1.5 and above, Thunderbird 1.5 and above, SeaMonkey 1.1 and above.
general. useragent. locale String ISO 639-2 value representing the user's language for the User-Agent string
general. useragent. override String A complete User-Agent string to use in place of the default.
general. useragent. security String Security level of the browser in the User-Agent string
N: No security
U (default): Strong security
I: Weak security
general. useragent. vendor String Vendor in the User-Agent string. Default value depends on browser (Firefox in Firefox 1.0).
Note: No longer specified by default in Firefox 1.5.
general. useragent. vendorSub String Vendor substring in the User-Agent string. Default value depends on browser version (1.0 in Firefox 1.0)
Note: No longer specified by default in Firefox 1.5.

Intl.

Name Type Meaning of Values
intl. accept_charsets String Currently unused. Previously: Character sets in which to accept data. Default value is iso-8859-1,*,utf-8.
intl. accept_languages String ISO 639-2 values of languages to accept. Default value is determined by localized information in chrome://navigator/locale/navigator.properties.
intl. charset. default String Determines the default character set. Default value is chrome://global-platform/locale/intl.properties
intl. charset. detector String Determines which locale URI sets how character set are detected in the browser
intl. charsetmenu. browser. cache String A comma-and-space-delimited list of cached character sets for the browser
intl. charsetmenu. browser. cache. size Integer Number of character sets to cache. Default value is 5.
intl. charsetmenu. browser. more* String A comma-and-space-delimited list of character sets to display in the character encoding menu
Note: In Firefox, these menus are viewable via "View → Character Encoding → More Encodings"
intl. charsetmenu. browser. static String A comma-and-space-delimited list of character sets to always display in the character encoding menu.
Note: In Firefox, this can be changed via "View → Character Encoding → Customize List"
intl. charsetmenu. browser. unicode String A comma-and-space-delimited list of Unicode character sets to display in the character encoding menu
Note: In Firefox, this menus is viewable via "View → Character Encoding → More Encodings → Unicode"
intl. charsetmenu. composer. cache String A comma-and-space-delimited list of cached character sets for Composer
intl. charsetmenu. mailedit String Determines the layout of the Character Coding menu in Mozilla Mail/News (message editor)
intl. charsetmenu. mailview. cache String A comma-and-space-delimited list of cached character sets for Mozilla Mail/News (main view)
intl. collationOption String A workaround to get correct column sorting in Mozilla Mail in Japanese builds of Linux. Default value is an empty string. Setting it to useCodePointOrder enables the workaround (see bug 18338).
intl. content. langcode String Default content language code
intl. fallbackCharsetList. (character set) String Determines the substitute character set if (character set) is unavailable.
intl. jis0208. map String Determines the map to use for JIS X 0208
CP932 (default in Windows): Use a CP932-compatible map
IBM943 (default in OS/2): Use an IBM943-compatible map
intl. keyboard. per_window_layout Boolean True: Allow different windows to retain their own keyboard locale settings (see bug 186549)
False (default): Opposite of the above
intl. locale. matchOS Boolean Determines how to decide locale
True: Use the locale the OS is using
False (default): Use the value set in general.useragent.locale.
intl. menuitems. alwaysappendaccesskeys String Specifies URI to determine if access keys are appended to menu items
intl. menuitems. insertseparatorbeforeaccesskeys String Specifies URI to determine if there is a space before the paranthesis of the accesskey in the menu's label (see bug 298712).

Javascript.

javascript.* has been migrated to Category:Preferences.

Layout.

layout.* allows you to modify selection behaviour, control spell checking in textareas, modify the appearance of unstyled XML, and change the way pages are layed out.

layout.* has been migrated to Category:Preferences.

Mail.

See Mail and news settings.

Mailnews.

See Mail and news settings.

Middlemouse.

middlemouse.* has been migrated to Category:Preferences.

Mousewheel.

mousewheel.* settings:

These fall into two groups: vertical and horizontal scrolling. The general form is:

  • mousewheel.(modifier key).(type)
  • mousewheel.horizscroll.(modifier key).(type)

Modifier key is one of: withaltkey, withcontrolkey, withmetakey, withnokey, or withshiftkey

Type is then one of:

action 
integer value that determines the type of action:
  • 0 - Scroll document by a number of lines (given by the numlines property)
  • 1 - Scroll document by one page
  • 2 - Move back/forward in history
  • 3 - Make text larger/smaller
  • 4 - Scroll document by a number of pixels (given by the numlines property)
numlines 
number of lines to scroll by if action is set to value 0, or pixels if action is set to value 4; otherwise, this value is ignored.
sysnumlines 
use system preferences to determine how many lines to scroll by

For example, to change (vertical) mousewheel scrolling to one page at a time -- set mousewheel.withnokey.action to 1

Network.

Name Type Meaning of Values
network. auth. use-sspi Boolean True (default in Windows): Use SSPI instead of GSSAPI for Kerberos-based authentication
False: Opposite of the above
Note: Firefox 1.5 and above only.
network. autodial-helper. enabled Boolean Help Windows NT, 2000, and XP dialup a RAS connection when a network address is unreachable.
True (default): Launch dialer (if one is configured) when address is unreachable
False: Display error message
network. automatic-ntlm-auth. allow-proxies Boolean Enable automatic use of the operating system's NTLM implementation to silently authenticate the user with their Windows domain logon with proxy servers. (See Integrated Authentication for more information)
True (default): Automatically authenticate with proxy servers
False: Prompt for authentication
network. automatic-ntlm-auth. trusted-uris String A comma-and-space-delimited list of URIs with which to automatically authenticate via NTLM (Windows domain logon). Default value is an empty string. (See Integrated Authentication for more information)
network. cookie. alwaysAcceptSessionCookies Boolean Determines whether to accept session cookies (kept for the duration of the browser session, then removed) if network.cookie.lifetimePolicy is 1.
True: Accept session cookies without prompting
False (default): Prompt before accepting session cookies
network. cookie. blockFutureCookies Boolean True: Allow sites to set cookies unless the user has removed cookies set by the site
False (default): Removed cookies do not affect future cookie acceptance.
network. cookie. cookieBehavior Integer Determines how the browser should handle cookies.
0 : Enable all cookies (default)
1: Allow cookies from originating server only
2: Disable all cookies
3: Use P3P policy to decide (Mozilla Suite/SeaMonkey only)
Note: In Firefox, this can be changed via "Tools → Options → Privacy → Cookies → Allow sites to set cookies / for the originating web site only" (Firefox 1.5 and below) or "Tools → Options → Privacy / Cookies → Accept cookies from sites" (Firefox 2); or, in Mozilla Suite/SeaMonkey, via Edit -> Preferences -> Privacy & Security -> Cookies / Cookie Acceptance Policy. Note: The option to limit cookies to the originating server was removed from the UI in Firefox 2.
network. cookie. denyRemovedCookies Boolean Seemingly unused.
network. cookie. disableCookieForMailNews Boolean Determines how Mozilla Mail/News should handle cookies.
True (default): Reject all cookies in Mozilla Mail/News
False: Accept cookies normally
network. cookie. enableForCurrentSessionOnly Boolean True: Delete all cookies at the end of the browser session
False (default): Opposite of the above
Note: This setting is deprecated in favor of network.cookies.lifetimePolicy (setting that to 2 is the equivalent of this preference set to True)
network. cookie. lifetime. days Integer Determines the number of days to keep cookies if network.cookie.lifetimePolicy is 3. Default value is 90.
network. cookie. lifetimePolicy Integer Determines how browser sets cookie lifetimes.
0 (default): Use supplied lifetime
1: Ask before accepting
2: Accept for session only
3: Cookies last for the number of days specified in network.cookie.lifetime.days
Note: In Firefox, this can be changed via "Tools → Options → Privacy → Cookies → Keep Cookies:" (Firefox 1.5 and below) or via "Tools → Options → Privacy / Cookies → Keep until:" (Firefox 2).
network. cookie. maxNumber Integer Determines the maximum amount of cookies to be stored. Valid range is from 0-65535 (RFC 2109 and RFC 2965 require this to be at least 300). Default value is 1000.
network. cookie. maxPerHost Integer Determines the maximum amount of cookies to be stored per host. Valid range is from 0-65535 (RFC 2109 and RFC 2965 require this to be at least 20). Default value is 50.
network. cookie. p3p String Determines the browser's P3P handling. An 8-character string. Default value is ffffaaaa. Each position in the string may be one of the following:
f: Flag the cookie
d: Accept the cookie, but downgrade it to a session-only lifetime
a: Accept the cookie
r: Reject the cookie
The character positions are as follows:
1st position: First party cookies from sites with no policy
2nd position: Third party cookies from sites with no policy
3rd position: First party cookies from sites that collect personal information without permission
4th position: Third party cookies from sites that collect personal information without permission
5th position: First party cookies from sites that collect personal information only with permission
6th position: Third party cookies from sites that collect personal information only with permission
7th position: First party cookies from sites that don't collect personal information
8th position: Third party cookies from sites that don't collect personal information
Note: P3P functionality is not present in Firefox and will probably be removed from Mozilla Suite (see bug 225287).
network. cookie. p3plevel Integer Security level of filtering for cookies
0: Low (use afafaaaa)
1 (default): Medium (use ffffaaaa)
2: High (use frfradaa)
3: Custom (use value in network.cookies.p3p)
Note: P3P functionality is not present in Firefox and will probably be removed from Mozilla Suite (see bug 225287).
network. cookie. prefsMigrated Boolean Indicates whether some cookie preferences — previously stored in deprecated preferences — have been migrated to current preferences.
True: Consult current preferences for cookie prefs
False (default): Read deprecated preferences, update current preferences, then set this preference to true
network. dir. format Integer How to format directory listings (e.g., from FTP servers)
1: Raw — exactly what comes off the network
2 (default): HTML
3: application/http-index-format (requires code to parse/display that is not present by default in Firefox; it is present in the Mozilla application suite)
network. dns. disableIPv6 Boolean Determines whether to perform IPv6 name lookups (see bug 68796)
True (default in OS X): Do not perform lookups
False (default in all others): Opposite of the above
network. dns. ipv4OnlyDomains String A comma-separated list of domains for which DNS lookups are for IPv4 addresses only (see bug 68796). Default value is .doubleclick.net.
network. dnsCacheEntries Integer Determines the maximum number of entries to keep in the DNS cache. Default value is 20.
network. dnsCacheExpiration Integer Determines the maximum number of seconds to cache resolved DNS entries. Default value is 60.
network. enableIDN Boolean Determines whether to use IDN (International Domain Name) support in the browser
True (default): Enable IDN support
False: Opposite of the above
Note: In Firefox 1.0, this preference did not "stick" (see bug 261934). Fixed in 1.0.1.
network. enablePad Boolean Determines whether the browser is allowed to perform proxy autodiscovery
True: Autodiscovery enabled
False (default): Opposite of the above
network. ftp. anonymous_password String Password to use when connecting to anonymous FTP servers. Sent instead of "mozilla@example.com" if advanced.mailftp is true. Not set by default.
network. ftp. idleConnectionTimeout Integer Time in seconds until an idle FTP connection is dropped. Default value is 300.
network. hosts. nntp_server String Pref to be removed (obsolete). Previously: News server for Mozilla Mail/News. Default value is news.mozilla.org.
network. hosts. pop_server String POP (incoming mail) server for Mozilla Mail/News. Default value is mail.
network. hosts. smtp_server String SMTP (outgoing mail) server for Mozilla Mail/News. Default value is mail.
network. http. accept-encoding String Comma-separated list of encoding types to accept from server. Sent with HTTP requests in Accept-Encoding header. Default value is gzip, deflate.
Note: compress is not a supported encoding (see bug 196406).
network. http. accept. default String Comma-separated list of MIME types to accept from server. Sent with HTTP requests in Accept header. Default value is text/xml,application/xml,application/xhtml+xml,text/html; q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5. (The space is actually not present and was only inserted to make it wrap.)
network. http. connect. timeout Integer Pref removed (unused). Previously: determines how long to wait for a response until registering a timeout. Default value is 30.
network. http. default-socket-type String Determines the socket type to be used for normal HTTP traffic. Default value is an empty string, indicating a normal TCP/IP socket type.
network. http. keep-alive Boolean Determines whether to use HTTP Keep-Alive connections. If more than one request is made, the browser attempts to reuse open connections that have been kept alive.
True (default): Send Connection: keep-alive header and Keep-Alive header based on contents of network.http.keep-alive.timeout
False: Opposite of the above (recommended in case of problems)
Note: This preference is effectively obsolete, as all connections are considered keep-alive in HTTP/1.1.
network. http. keep-alive. timeout Integer Requested timeout for Keep-Alive connections in seconds. Default value is 300.
network. http. max-connections Integer Determines the maximum number of simultaneous HTTP connections. Default value is 30. Valid values are between 1 and 65535 inclusive.
network. http. max-connections-per-server Integer Determines the maximum number of simultaneous HTTP connections that can be established per host. If a proxy server is configured, then the server is the proxy server. Default value is 15. Valid values are between 1 and 255 inclusive.
network. http. max-persistent-connections-per-proxy Integer If network.http.keep-alive is true, and if a proxy server is configured, then a new connection will only be attempted if the number of active persistent connections to the server is less than this preference. Default value is 8. Valid values are between 1 and 255 inclusive.
network. http. max-persistent-connections-per-server Integer If network.http.keep-alive is true, and if a proxy server is not configured, then a new connection will only be attempted if the number of active persistent connections to the server is less than this preference. Default value is 6. Valid values are between 1 and 255 inclusive.
network. http. phishy-userpass-length Integer A number between 0 and 255. Warn the user if we load an URL containing a userpass field (e.g., http://user:pass@example.com/) unless its length is less than this threshold. Default value is 1.
network. http. pipelining Boolean Determines whether to use HTTP/1.1 pipelining.
True: Enable pipelining
False (default): Disable pipelining
Note: Pipelining is not well-supported by some servers and proxies. Things may break — use with caution.
network. http. pipelining. firstrequest Boolean Pref removed (unused)
network. http. pipelining. maxrequests Integer Determines the maximum number of HTTP requests in the pipeline (sent sequentially without waiting for a response). Values greater than 8 are assumed to be 8; values less than 1 are assumed to be 1. Default value is 4.
network. http. proxy. keep-alive Boolean Determines whether to use HTTP Keep-Alive connections when a proxy server is configured. If more than one request is made, the browser attempts to reuse open connections that have been kept alive.
True (default): Send Connection: keep-alive header and Keep-Alive header based on contents of network.http.keep-alive.timeout
False: Opposite of the above (recommended in case of problems)
Note: This preference is effectively obsolete, as all connections are considered keep-alive in HTTP/1.1.
network. http. proxy. pipelining Boolean Determines whether to use HTTP/1.1 pipelining when a proxy server is configured.
True: Enable pipelining
False (default): Disable pipelining
Note: Pipelining is not well-supported by some servers and proxies. Things may break — use with caution.
network. http. proxy. version String Determines which HTTP version to use when a proxy server is configured. Default value is 1.1, though 1.0 is recommended for some finnicky proxies (such as the Junkbuster proxy).
network. http. redirection-limit Integer Determines how many consecutive HTTP redirects the browser will follow. Default value is 20. Setting it to 0 will stop all redirects from occuring.
Note: These are header-based redirects, not (for example) <meta http-equiv="refresh"> HTML-based redirects.
network. http. request. max-start-delay Integer Determines amount of time (in seconds) to suspend pending requests, before spawning a new connection, once the limit on the number of persistent connections per host (network.http.max-persistent-connections-per-server) has been reached. However, a new connection will not be created if max-connections (network.http.max-connections) or max-connections-per-server (network.http.max-connections-per-server) has also been reached. Default value is 10.
network. http. request. timeout Integer Pref removed (unused). Previously: HTTP-specific network timeout. Default value is 120.
network. http. sendRefererHeader Integer Determines when to send the Referer HTTP header.
0: Never send the referring URL
1: Send only on clicked links
2 (default): Send for links and images
network. http. sendSecureXSiteReferrer Boolean Determines how to handle Referer HTTP header when navigating between secure (HTTPS) hosts.
True (default): Send referring URL normally (default for compatibility reasons, see bug 141641)
False: Send no referring URL
network. http. use-cache Boolean Determines whether to enable caching of HTTP documents.
True (default): Enable caching
False: Opposite of the above
network. http. version String Determines which HTTP version to use. Default value is 1.1.
network. IDN_show_punycode Boolean Determines how to display IDN hostnames in the Location Bar (see bug 282270).
True (default): All IDN (UTF-8) domain names will be normalized to punycode.
False: Display IDN domain names in UTF-8
Note: Addresses may be input as UTF-8 regardless of this setting.
network. IDN. blacklist_chars String If a domain name contains any of the characters in this preference's value, display the domain in punycode, overriding network.IDN_show_punycode and network.IDN.whitelist (see bug 301694). See here for a complete list of characters in the default preference.
Note: Firefox 1.5 and above only.
network. IDN. whitelist. (TLD) Boolean When network.IDN_show_punycode is false, these preferences are checked against the top-level domain of any IDN domain name. If there is a whitelist entry for the top-level domain and the entry is set to true, then the IDN is shown as intended. Otherwise, it is shown in punycode. By default, the top-level domains ac, at, br, ch, cl, cn, de, dk, fi, gr, hu, info, io, jp, kr, li, lt, museum, no, se, sh, th, tm, tw, and vn are whitelisted (set to true).
Note: Firefox 1.5 and above only.
network. image. imageBehavior Integer Determines when images should be loaded.
0 (default): Load all images
1: Load images from same (originating) server only
2: Do not load any images
Note: In Firefox, this can be changed via "Tools → Options → Web Features → Load Images / for the originating web site only"
In Firefox 1.5 and above, this preference has been renamed to permissions.default.image.
network. image. warnAboutImages Boolean Pref unused (feature disabled). Previously:
Determines whether to prompt the user before loading an image.
True: Load no images until user confirms
False (default): Load images normally
network. manage-offline-status Boolean (Applies to Firefox 3.5 and above)
Determines whether Firefox is allowed to automatically set itself to offline mode in response to certain Web sites, or if the network connection is interrupted. (See bug 620472 and this and following messages for more information.)
True (implicit default in Firefox 3.5 and 3.6): Allows automatically setting offline mode.
False (default in Firefox 4): Prevents automatically setting offline mode.
True in SeaMonkey 2.0 and above but SeaMonkey and Thunderbird have a separate offline manager as part of MailNews.
network. negotiate-auth. allow-proxies Boolean True (default): Allow SPNEGO by default when challenged by a proxy server. (See Integrated Authentication and bug 266485 for more information.)
False: Opposite of the above
network. negotiate-auth. delegation-uris String A comma-and-space-delimited list of sites for which the browser may delegate user authorization to the server. (See Integrated Authentication for more information.) Default value is an empty string.
network. negotiate-auth. gsslib String Path to a specific GSSAPI library. Allows the browser (e.g.) to load different Kerberos implementations at the user's request. Default value is an empty string.
Note: See bug 295109 for more information.
network. negotiate-auth. trusted-uris String A comma-and-space-delimited list of sites that are permitted to engage in SPNEGO authentication with the browser. (See Integrated Authentication for more information.) Default value is an empty string.
network. negotiate-auth. using-native-gsslib Boolean True (default): Use the GSS lib that comes standard with the host operating system
False: Use the GSSAPI library specified in network.negotiate-auth.gsslib.
network. ntlm. send-lm-response Boolean Determines whether or not the LM hash will be included in response to a NTLM challenge. Servers should almost never need the LM hash, and the LM hash is what makes NTLM authentication less secure.
True: Send the LM hash
False (default): Opposite of the above
Note: Does not affect network.automatic-ntlm-auth.* settings. See bug 250961 for more information.
network. online Boolean Indicates whether the user is currently online. Used for enabling/disabling various options in the UI.
True (default): User is online
False: Opposite of the above
network. prefetch-next Boolean Determines whether to use link prefetching.
True (default): Silently prefetch hinted documents and store in the cache
False: Disable all link prefetching
network. protocol-handler. app. (protocol) String The path and program to run for the specified protocol.
Note: To set up a new protocol, it must be registered. See here for more information.
network. protocol-handler. expose-all Boolean Determines whether to expose (enable) all protocol handlers. This preference overrides more specific preferences, e.g. network.protocol-handler.expose.mailto.
True: Try to open link clicks in browser first, then fail over to system handlers
False: Do not expose all protocol handlers
network. protocol-handler. expose. (protocol) Boolean Determines whether to expose (enable) the specified protocol handler. These preferences are overridden by network.protocol-handler.expose-all.
True: Try to open link clicks in browser firsst, then fail over to system handlers
False: Do not expose this protocol handler
network. protocol-handler. external-default Boolean Determines the default action for unlisted external protocol handlers
True (default): Try to load
False: Opposite of the above
network. protocol-handler. external. (protocol) Boolean Determines whether to allow external protocol handlers to catch links with these protocols
True: Allow external handler to handle link
False (default): Prevent external handler from handling this link
network. protocol-handler. warn-external-default Boolean Determines whether to warn the user before loading an unlisted external handler
True (default): Warn the user
False: Opposite of the above
network. protocol-handler. warn-external. (protocol) Boolean Determines whether to warn the user before loading this protocol's external handler
True: Warn the user
False (default): Opposite of the above
network. proxy. autoconfig_url String The automatic proxy configuration URL used by the browser to determine a proxy server. Used when network.proxy.type is 2. Default value is an empty string.
Note: In Firefox, this can be changed via "Tools → Options → Advanced → Network (Firefox 1.5 and 1.0.x: General) → Connection Settings... → Automatic proxy configuration URL"
network. proxy. failover_timeout Integer Determines how long to wait until re-contacting an unresponsive proxy server. Default value is 1800 (30 minutes).
network. proxy. (protocol) String A manually configured proxy for the given protocol. Default value is an empty string.
Note: In Firefox, this can be changed via "Tools → Options → General (Firefox 2.0+: Advanced → Network) → Connection Settings... → Manual proxy configuration"
network. proxy. (protocol)_port Integer The port for the manually configured proxy for the given protocol. Used when network.proxy.type is 1.
Note: In Firefox, this can be changed via "Tools → Options → General (Firefox 2.0+: Advanced → Network) → Connection Settings... → Manual proxy configuration"
network. proxy. no_proxies_on String A comma-and-space-delimited list of hosts for which the specified proxies should not be used. (See No proxy for for syntax.)
Note: In Firefox, this can be changed via "Tools → Options → General (Firefox 2.0+: Advanced → Network) → Connection Settings... → Manual proxy configuration → No Proxy for"
network. proxy. share_proxy_settings Boolean Determines whether to use the same proxy server for all protocols.
True: Use one proxy for all protocols
False (default): Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → General (Firefox 2.0+: Advanced → Network) → Connection Settings... → Manual proxy configuration → Use the same proxy for all protocols"
network. proxy. socks_remote_dns Boolean True: Perform all DNS lookups on remote proxy server (see bug 134105)
False (default): Perform all DNS lookups client-side
network. proxy. socks_version Integer Determines which version of SOCKS to use with the server specified in network.proxy.socks. Default value is 5. (The only other valid version is 4.)
network. proxy. type Integer Determines how the browser uses proxies.
0 (default): Direct connection to the Internet (no proxy used)
1: Manual proxy configuration (use values in network.proxy.*)
2: Autoconfiguration by URL (use value in network.proxy.autoconfig_url)
3: Same as 0 for compatibility reasons (see bug 115720) and will be reset to 0
4: Auto-detect proxy settings for this network
network. security. ports. banned String A comma-separated list of port numbers to disable in addition to the ports already disabled by default. (See Mozilla Port Blocking for more information.)
network. security. ports. banned. override String A comma-separated list of port numbers to enable, overriding the default port blocking. (See Mozilla Port Blocking for more information.)
network. standard-url. encode-utf8 Boolean Determines how URLs are encoded and sent
True: Always encode and send URLs as UTF-8
False (default in Firefox 1.0.x): Opposite of the above
Note: This was True for a short time before Firefox 1.5, causing trouble with some international websites (see bug 284474)
network. standard-url. escape-utf8 Boolean Determines whether URLs with UTF-8 characters are escaped per the spec
True (default): Escape UTF-8 characters
False: Send URLs as they are

News.

See Mail and news settings.

NGLayout.

NGLayout stands for Next Generation Layout Engine. These preferences are largely low-level tweaks and debug options for how content appears in the browser.

Name Type Meaning of Values
nglayout. compatibility. mode Integer Force a compatibility mode instead of autodetecting.
0 (default): Use supplied DTD
1: Standards compliance mode
2: Quirks mode
nglayout. debug. checksum_xul_fastload_file Boolean True (default): Verify that the checksum of the XUL Fastload file hasn't changed since that file was last written to disk
False: Don't bother verifying the checksum
nglayout. debug. crossing_event_dumping Boolean True: In debug-enabled builds, output information about NS_MOUSE_ENTER/EXIT-related events to stdout when Caps Lock is on and nglayout.debug.event_dumping is true
False (default): Opposite of the above
nglayout. debug. disable_xul_cache Boolean True: Prevent Mozilla from caching any chrome-level XUL components (XUL, JavaScript, CSS).
False (default): Cache XUL components for better performance.
nglayout. debug. disable_xul_fastload Boolean True: Disable XUL Fastload caching the in-memory compiled XUL to file (xul.mfl, xul.mfasl)
False (default): Enable XUL Fastload (see bug 112064)
nglayout. debug. enable_xbl_forms Boolean True: Use XBL form controls
False (default): Opposite of the above
nglayout. debug. event_dumping Boolean True: In debug-enabled builds, output event-related information to stdout when Caps Lock is on
False (default): Opposite of the above
nglayout. debug. invalidate_dumping Boolean True: In debug-enabled builds, output information about invalidated objects/elements to stdout when Caps Lock is on
False (default): Opposite of the above
nglayout. debug. motion_event_dumping Boolean True: In debug-enabled builds, output information about NS_MOUSE_MOVE-related events to stdout when Caps Lock is on and nglayout.debug.event_dumping is true
False (default): Opposite of the above
nglayout. debug. paint_dumping Boolean True: In debug-enabled builds, output information about paint events to stdout when Caps Lock is on
False (default): Opposite of the above
nglayout. debug. paint_flashing Boolean True: In debug-enabled builds, flash painted elements/objects when Caps Lock is on
False (default): Opposite of the above
nglayout. events. dispatchLeftClickOnly Boolean Determines whether to dispatch left-click events only to content in the browser (chrome/XUL is exempt from the effects)
True (default): Dispatch only left-click events to browser content
False: Dispatch both left- and middle-click events
nglayout. initialpaint. delay Integer Determines time in milliseconds to wait before an initial reflow attempt during page rendering. Default value is 250 (PAINTLOCK_EVENT_DELAY). Synchronize with content.notify.interval for best performance.

Plugin.

Name Type Meaning of Values
plugin. default_plugin_disabled Boolean True (default): When a plugin is needed, prompt the user
False: Don't prompt the user to install needed plugins
plugin. disable_full_page_plugin_for_types String MIME types that would normally be opened with a plugin, except that the action has been changed in the Firefox Download Actions window. Resetting this preference changes the download action back to the plugin.
plugin. expose_full_path Boolean True: In about:plugins and navigator.plugins, reveal the full path to plugin files
False (default): Show only the plugin filename
plugin. override_internal_types Boolean True: Allow plugins to override internal imglib decoder MIME types in full-page mode
False (default): Opposite of the above
plugin. scan. 4xPluginFolder Boolean Controls the scanning of the Navigator 4.x directory for plugins. When this preference is missing, the default is to pickup popular plugins such as Flash, Shockwave, Acrobat, and Quicktime. If set to true, ALL plugins will be picked up and if set to false the scan will not happen at all.
plugin. scan. (Plugin) String Name of plugin to scan for, with a minimum version specified. By default, this preference exists for Acrobat (5.0), QuickTime (5.0), SunJRE (1.3), and WindowsMediaPlayer (7.0).
plugin. scan. plid. all Boolean True (default): Locate plugins by the directories specified in the Windows registry for PLIDs (currently HKLM\Software\MozillaPlugins\xxxPLIDxxx\Path)
False: Opposite of the above

Print.

Name Type Meaning of Values
print. always_cache_old_pres Boolean True: Cache old presentation when going into Print Preview
False (default): Opposite of the above
print. extend_native_print_dialog Boolean True (default): Extend the native dialog with information on printing frames.
False: Opposite of the above
Note: Firefox 1.5 and above only.
print. postscript.enabled Boolean True (default): Enable the the Postscript printing system on Linux, Unix, or VMS.
False: Disable the system.
print. postscript.cups.enabled Boolean True (default): Enable CUPS support within the Postscript printing system.
False: Do not try to access CUPS.
print. print_edge_(position) Integer Determines the distance from the (position) edge of the page to measure the margin. Default value is 0.
print. print_extra_margin Integer Determines an extra gap or margin in twips (90 twips is 1/8 of an inch) around the content of the page for Print Preview only. Default value is 90 (1/8").
print. print_(footer or header)(position) String At the given position in the header or footer, print one of the following:
&T: Title of the document
&U: URL
&D: Date/time
&P: Page number
&PT: Page number "of" total pages
(any string): A literal string with the above substitutions made
print. printer_list String Manually supplied list of printers for the Postscript printing system on Linux, Unix, or VMS.
print. save_print_settings Boolean True (default): Save the print settings after each print job
False: Opposite of the above
print. show_print_progress Boolean True (default): Show the progress dialog when printing
False: Opposite of the above
print. use_global_printsettings Boolean True (default): Every browser window uses the same print settings
False: Each browser window uses its own settings, and changes in one window don't affect the others
print. use_native_print_dialog Boolean True (default): Use the native print dialog
False: Use the OS print dialog
Note: Windows-only
print. whileInPrintPreview Boolean True (default): Allow printing while in Print Preview screen
False: Opposite of the above

Privacy.

Name Type Meaning of Values
privacy. item. cache Boolean True (default): Clear the cache when using the Clear Private Data feature (Firefox 1.5 and above only)
False: Do not clear the cache
Note: This can be changed via "Tools → Options → Privacy → Settings..." (Firefox 1.5) or "Tools → Options → Privacy / Private Data → Settings..." (Firefox 2.0 and above).
privacy. item. cookies Boolean True: Delete all cookies when using the Clear Private Data feature (Firefox 1.5 and above only)
False (default): Opposite of the above
Note: This can be changed via "Tools → Options → Privacy → Settings..." (Firefox 1.5) or "Tools → Options → Privacy / Private Data → Settings..." (Firefox 2.0 and above).
privacy. item. downloads Boolean True (default): Clear history of downloaded files when using the Clear Private Data feature (Firefox 1.5 and above only)
False: Opposite of the above
Note: This can be changed via "Tools → Options → Privacy → Settings..." (Firefox 1.5) or "Tools → Options → Privacy / Private Data → Settings..." (Firefox 2.0 and above).
privacy. item. formdata Boolean True (default): Clear all saved form data when using the Clear Private Data feature (Firefox 1.5 and above only)
False: Opposite of the above
Note: This can be changed via "Tools → Options → Privacy → Settings..." (Firefox 1.5) or "Tools → Options → Privacy / Private Data → Settings..." (Firefox 2.0 and above).
privacy. item. history Boolean True (default): Clear the browsing history when using the Clear Private Data feature (Firefox 1.5 and above only)
False: Opposite of the above
Note: This can be changed via "Tools → Options → Privacy → Settings..." (Firefox 1.5) or "Tools → Options → Privacy / Private Data → Settings..." (Firefox 2.0 and above).
privacy. item. offlineApps Boolean True: Clear the offline website data when using the Clear Private Data feature (Firefox 3 and above only)
False (default): Opposite of the above
Note: This can be changed via "Tools → Options → Privacy / Private Data → Settings...".
privacy. item. passwords Boolean True: Delete all saved passwords when using the Clear Private Data feature (Firefox 1.5 and above only)
False (default): Opposite of the above
Note: This can be changed via "Tools → Options → Privacy → Settings..." (Firefox 1.5) or "Tools → Options → Privacy / Private Data → Settings..." (Firefox 2.0 and above).
privacy. item. sessions Boolean True (default): Clear all authenticated SSL sessions when using the Clear Private Data feature (Firefox 1.5 and above only)
False: Opposite of above
Note: This can be changed via "Tools → Options → Privacy → Settings..." (Firefox 1.5) or "Tools → Options → Privacy / Private Data → Settings..." (Firefox 2.0 and above).
privacy. item. siteprefs Boolean Planned for future use.
privacy.popups. disable_from_plugins Integer Sets limits on popups generated from plugins (e.g. Flash)
0: lets all popups through
1: limits their number to dom.popup_maximum (even with popup blocker disabled)
2: (default in Firefox 1.5 and above and SeaMonkey) blocks popups from plugins. Whitelisted sites will still be able to open popups, regardless of this setting.
3: Blocks all plugin-initiated popups, even those on whitelisted sites.
privacy. popups. firstTime Boolean True (default): The user has never hidden the popup blocker notification bar before, so show a dialog explaining the status bar icon
False: The user has been informed of the status bar icon
privacy. popups. policy Integer Determines the popup blocker behavior.
1: Allow popups
2: Reject popups
Note: Seems to be deprecated in favor of dom.disable_open_during_load
privacy. popups. showBrowserMessage Boolean True (default): Display a message at the top of the browser window when a popup has been blocked
False: Display a status bar icon to indicate when a popup has been blocked
privacy. popups. usecustom Boolean Seemingly unused.
privacy. sanitize. promptOnSanitize Boolean True (default): Prompt before performing the Clear Private Data operation (Firefox 1.5 and above only)
False: Clear Private Data without confirmation
Note: In Firefox 1.5 and above, this can be changed via "Tools → Options → Privacy → Settings..."
privacy. sanitize. sanitizeOnShutdown Boolean True: Perform the Clear Private Data operation when closing the browser (Firefox 1.5 and above only)
False (default): Clear Private Data only when asked
Note: In Firefox 1.5 and above, this can be changed via "Tools → Options → Privacy → Settings..."

Profile.

Name Type Meaning of Values
profile. allow_automigration Boolean Determines how the Profile Manager handles automigration of Netscape 4.x profiles
True: Allow automigration
False (default): Opposite of the above
Note: Has no effect since Gecko 1.9.0 (Firefox 3.0, SeaMonkey 2.0, Thunderbird 3.0).
profile. confirm_automigration Boolean True (default): Ask user before performing an automigration
False: Opposite of the above
profile. manage_only_at_launch Boolean True: Only show the Profile Manager at program launch
False (default): Show Profile Manager at any time via menus
Note: In Firefox, there is no UI to access the Profile Manager from within the browser
profile. migration_behavior Integer Determines how the profile root is set.
0 (default): use NS_APP_USER_PROFILES_ROOT_DIR
1: create one based on the NS4.x profile root
2: Use value in profile.migration_directory (if empty, use NS_APP_USER_PROFILES_ROOT_DIR)
profile. migration_directory String Path to directory for migration. Default value is an empty string.
profile. seconds_until_defunct Integer Number of seconds to wait until the profile is considered defunct. Default value is -1 (never consider the profile defunct).

Security.

Name Type Meaning of Values
security. OCSP. URL String Determines the URL to query for OCSP certificate verification/validation if security.OCSP.enabled is 2. Default value is an empty string.
Notes: In Firefox, this can be changed via "Tools → Options → Advanced → Validation → OCSP → Service URL".
In SeaMonkey 2, this can be changed via "Edit → Preferences → Privacy & Security → Validation → OCSP → Validate all certificates using the following OCSP server → Service URL".
security. OCSP. enabled Integer Determines behavior of OCSP-based certificate verification/validation.
0 (default in Firefox 2 and below): Do not use OCSP for certificate validation
1 (default in Firefox 3 and above): Use OCSP to validate only certificates that specify an OCSP service URL (see bug 110161).
2: Enable and use values in security.OCSP.URL and security.OCSP.signingCA for validation.
Notes: In Firefox, this can be changed via "Tools → Options → Advanced → Validation → OCSP".
In SeaMonkey 2, this can be changed via the first checkbox and the radio buttons under "Edit → Preferences → Privacy & Security → Validation → OCSP".
security. OCSP. signingCA String Determines the name of the OCSP signing certificate authority to use if security.OCSP.enabled is 2. Default value is an empty string.
Notes: In Firefox, this can be changed via "Tools → Options → Advanced → Validation → OCSP → Response Signer".
In SeaMonkey 2, this can be changed via "Edit → Preferences → Privacy & Security → Validation → OCSP → Validate all certificates using the following OCSP server → Response Signer".
security. ask_for_password Integer Determines when Mozilla Mail should ask for the master password.
0 (default): Only the first time it's needed
1: Every time it's needed
2: Every n minutes, where n is the value in security.password_lifetime.
security. checkloaduri Boolean Pref removed (use CAPS instead). Previously:
Determines how to handle access across schemes (e.g., loading file: URLs from http: URLs)
True (default): Perform security checks and block access for insecure access
False: Opposite of the above
security. default_personal_cert String Determines the selection of a security certificate to present to web sites that require one.
Select Automatically (default): Automatically choose the certificate
Ask Every Time: Prompt user with a choice of certificate options every time
Note: In Firefox, this can be changed via "Tools → Options → Advanced → Certificates → Client Certificate Selection"
security. dialog_enable_delay Integer Amount of time in milliseconds to disable buttons on security-sensitive dialog boxes. Default value is 2000.
security. directory String Seemingly unused.
security. enable_java Boolean True (default): Java is enabled
False: Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Content (Web Features in Firefox 1.0.x) → Enable Java"
security. enable_ssl2 Boolean True (default in Firefox 1.5 and below): SSL 2.0 is enabled
False (default in Firefox 2): Opposite of the above
Note: In Firefox 1.5 and below, this can be changed via "Tools → Options → Advanced → Security → Use SSL 2.0" (removed from the UI in Firefox 2).
security. enable_ssl3 Boolean True (default): SSL 3.0 is enabled
False: Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Advanced → Security → Use SSL 3.0"
security. enable.tls Boolean True (default): TLS 1.0 is enabled
False: Opposite of the above
Note: In Firefox, this can be changed via "Tools → Options → Advanced → Security → Use TLS 1.0"
security. password_lifetime Integer Determines how long (in minutes) to go without asking for the master password in Mozilla Mail when security.ask_for_password is 2. Default value is 30.
security. (ssl2 or ssl3). (cipher suite) Boolean True (default in all except the two below): The SSL 2.0 encryption type (cipher suite) is enabled
False: Opposite of the above
security. ssl3. rsa_null_sha Boolean True: Enable "No encryption with RSA authentication and an SHA-1 MAC" as a cipher suite
False (default): Opposite of the above
security. ssl3. rsa_null_md5 Boolean True: Enable "No encryption with RSA authentication and an MD5 MAC" as a cipher suite
False (default): Opposite of the above
security. ui. enable Boolean Pref removed
security. warn_entering_secure Boolean True (default): Display a dialog warning the user when entering a secure site from an insecure one
False: Opposite of the above
security. warn_entering_secure. show_once Boolean True (default): Leave the "Alert me whenever..." box unchecked on the security warning dialog
False: Opposite of the above
security. warn_entering_weak Boolean True (default): Display a dialog warning the user when entering an insecure site from a secure one
False: Opposite of the above
security. warn_entering_weak. show_once Boolean True (default): Leave the "Alert me whenever..." box unchecked on the security warning dialog
False: Opposite of the above
security. warn_leaving_secure Boolean True (default): Display a dialog warning the user when leaving a secure site
False: Opposite of the above
security. warn_leaving_secure. show_once Boolean True (default): Leave the "Alert me whenever..." box unchecked on the security warning dialog
False: Opposite of the above
security. warn_submit_insecure Boolean True (default): Display a dialog warning the user when submitting a form to an insecure site
False: Opposite of the above
security. warn_submit_insecure. show_once Boolean True (default): Leave the "Alert me whenever..." box unchecked on the security warning dialog
False: Opposite of the above
security. warn_viewing_mixed Boolean True (default): Display a dialog warning the user when a page has both encrypted and non-encrypted content
False: Opposite of the above
security. warn_viewing_mixed. show_once Boolean True (default): Leave the "Alert me whenever..." box unchecked on the security warning dialog
False: Opposite of the above
security. xpconnect. plugin. unrestricted Boolean True (default): Allow scripting of plugins by untrusted scripts
False: Opposite of the above

Signon.

Name Type Meaning of Values
signon. prefillForms Boolean True (default): Allows auto-filling of stored usernames and passwords on webpage forms
False: Opposite of the above
Added in Firefox 1.5.0.9 and 2.0.0.1; set to "False" as workaround for bug 360493
signon. SignonFileName String Determines the filename that the Password Manager uses for storing signon data. Default value is signons.txt
signon. SignonFileName2 String Determines the filename that the Password Manager uses for storing signon data starting in Firefox 1.5.0.10 and Firefox 2.0.0.2 (bug 360493). Default value is signons2.txt
signon.expireMasterPassword Boolean True: The master password for the Password Manager will expire
False (default): Opposite of the above
signon. rememberSignons Boolean True: (default): Enable the Password Manager
False Opposite of the above

Snav.

These preferences are associated with Spatial Navigation, a method of moving focus on a web page with respect to the visual layout of elements. Spatial navigation is not present (compiled in) by default, so these preferences will only work in binaries compiled with ac_add_options --enable-extensions=spatialnavigation.

Name Type Meaning of Values
snav. directionalBias Integer When calculating distances between elements on the screen, elements may be given a bias if the elements are in the direction of navigation. The bias is a given by a fraction such that:
bias distance = true distance / directional bias. The default value is 3.
snav. disableJS Boolean True (default): Disable onFocus event that an element may recieve during spatial navigation. On some pages the page decides to move the focus as if the targeted content was clicked. This may lead to an undesirable behavior.
False: Honor onFocus handlers triggered by spatial navigation
snav. enabled Boolean True (default): Enable spatial navigation
False: Opposite of the above
snav. ignoreTextFields Boolean True (default): Ensure that text fields and inputs retain focus even if spatial navigation was requested
False: Opposite of the above
snav. keyCode. down String Determines the key code corresponding to downwards spatial navigation. Default value is DOM_VK_DOWN. (A complete listing of possible key codes is available in nsIDOMKeyEvent.idl.)
snav. keyCode. left String Determines the key code corresponding to left spatial navigation. Default value is DOM_VK_LEFT. (A complete listing of possible key codes is available in nsIDOMKeyEvent.idl.)
snav. keyCode. modifier String Determines the key code corresponding to the required modifier keys. These values are given as follows:
NONE: 0
SHIFT: 0x00100000
CONTROL: 0x00001100
ALT: 0x00000012
The default value is ALT | SHIFT.
snav. keyCode. right String Determines the key code corresponding to right spatial navigation. Default value is DOM_VK_RIGHT. (A complete listing of possible key codes is available in nsIDOMKeyEvent.idl.)
snav. keyCode. up String Determines the key code corresponding to upwards spatial navigation. Default value is DOM_VK_LEFT. (A complete listing of possible key codes is available in nsIDOMKeyEvent.idl.)
snav. rectFudge Integer To reduce the chance that a element overlaps with another element, we reduce the elements height and width by this value. Default value is 20.

Toolkit.

Name Type Meaning of Values
toolkit. autocomplete. richBoundaryCutoff Integer Determines how much of the text to search for matched text, specified as the number of characters from the beginning. Default is 200.
toolkit. scrollbox. clickToScroll. scrollDelay Integer Determines how many milliseconds to wait before scrolling the tab strip by another increment. (Default: 150)
toolkit. scrollbox. scrollIncrement Integer Determines how many pixels to scroll at a time when scrolling the tab strip’s scrollbox. (Default: 20)
toolkit. scrollbox. smoothScroll Boolean True (default): Scroll the tab strip smoothly to a newly-selected tab.
False: Move to the new tab immediately.
toolkit. storage. synchronous Integer Specify the SQLite disk sync mode to use.

0: risky sync mode. May cause database corruption if the OS crashes or the computer loses power.
1 (default): safe sync mode.
2: extra-slow-extra-safe sync mode.

This preference was added in bug 421482. At the same time, Firefox was modified to use mode 1 instead of mode 2 by default, to improve performance.[9] (Firefox 3)

toolkit. zoomManager. zoomValues String Specify the zoom levels as multipliers that the user can use on content. Default value is .3,.5,.67,.8,.9,1,1.1,1.2,1.33,1.5,1.7,2,2.4,3

UI.

Most of these preferences control settings that the browser attempts to read from the host operating system (e.g., your current color scheme). However, these can be overridden by manually setting the preferences to something else. For a more complete listing of the UI.* preferences, see UI Widget Look and Feel.

Name Type Meaning of Values
ui. key. accelKey Integer Determines the key code corresponding to the accelerator key.
17 (default in Windows): Ctrl
18 (default in BeOS): Alt
224 (default in Mac OS X): Cmd
ui. key. generalAccessKey Integer Determines the key code corresponding to the generic key used for Mozilla shortcuts
-1 (default in recent builds) Use ui. key. chromeAccess for chrome and ui. key. contentAccess for content
0 Disable
17 (default in BeOS, Mac OS X): Ctrl
18 (default in Windows): Alt
ui. key. chromeAccess Integer Determines the key accelerator for chrome shortcuts
0 Disable
1 Shift
2 Ctrl (default in Mac OS X)
4 Alt (default in Windows and Linux)
8 Meta or Cmd
Other: Add the above for keychords
ui. key. contentAccess Integer Determines the key accelerator for shortcuts in content
0 Disable
1 Shift
2 Ctrl (default in Mac OS X)
4 Alt
8 Meta or Cmd
Other: Add the above for keychords. E.g. 5 = Alt+Shift (default in Windows and Linux)
ui. key. menuAccessKey Integer Determines the key code corresponding to Mozilla menu access
0 (default in Mac OS X): none
17 (default in BeOS): Ctrl
18 (default in Windows): Alt
ui. key. menuAccessKeyFocuses Boolean True (default in Windows): Menus gain focus when ui.key.menuAccessKey is pressed
False: Opposite of the above
ui. key. saveLink. shift Boolean True (default): Shift-clicking a link opens the Save Link As dialog
False: Opposite of the above
ui. submenuDelay Integer Determines the delay in milliseconds between hovering over a menu option with a submenu and the submenu appearing. If this preference is not set, the OS's value is used.
ui. textSelectBackground String Determines the background color to use for text selections as a hex code or named color. If this preference is not set, the OS's value is used.
ui. textSelectBackgroundAttention String Determines the background color used for Find As You Type as a hex code or named color. If this preference is not set, the inverse of ui.textSelectBackground is used.
ui. textSelectForeground String Determines the text color to use for text selections as a hex code or named color. If this preference is not set, the OS's value is used.

Update. and Update_notifications.

Name Type Meaning of Values
update. interval Integer Determines how often to check extensions.update.interval and app.update.interval in milliseconds. Default value is 3600000 (1 hour).
update. severity Integer Used by the update system to determines when to display the icon for pending updates.
0 (default): Low severity update(s) available (extension/theme updates)
1: Medium severity update(s) available (numerous extension/theme updates)
2: High severity updates available (new version of Firefox/security patch)
update. showSlidingNotification Boolean True (default): Display the sliding alert when updates are available
False: Opposite of the above
update_notifications. enabled Boolean True (default): Display a notification in the browser when updates are available
False: Opposite of the above
update_notifications. provider. 0. datasource String Determines where to get update notifications. Value is pulled from chrome://browser-region/locale/region.properties.
update_notifications. provider. 0. frequency Integer Number of days between update checks. Default value is 7.

View_source.

Name Type Meaning of Values
view_source. editor. external Boolean True: The program defined in view_source. editor. path should be used when View Source is requested. False (default): The internal viewer should be used when View Source is requested.
view_source. editor. path String Path to the external editor to use for View Source when view_source. editor. external is True. If the path doesn't exist or isn't a program, the internal viewer will always be used.
view_source. syntax_highlight Boolean True (default): Enable syntax highlighting in the view source window.
False: Opposite of the above
Note: This can be changed via "View → Syntax Highlighting" in the view source window.
view_source. tab_size Integer sets the width of a tab character in the view source window. Already open windows aren't updated (implemented in bug 295506 in trunk builds (mozilla-1.9.3a1) starting 2010-02-03)
view_source. wrap_long_lines Boolean True: HTML code will wrap in the view source window.
False (default): HTML code will not wrap in the view source window.
Note: This can be changed via "View → Wrap Long Lines" in the view source window.

XPInstall.

Name Type Meaning of Values
xpinstall. dialog. confirm String Determines the chrome location of the XPInstall dialog. Default value is chrome://mozapps/content/xpinstall/xpinstallConfirm.xul.
xpinstall. dialog. progress. chrome String Determines the chrome location of the extensions dialog. Default value is chrome://mozapps/content/extensions/extensions.xul?type=extensions.
xpinstall. dialog. progress. skin String Determines the chrome location of the themes dialog. Default value is chrome://mozapps/content/extensions/extensions.xul?type=themes.
xpinstall. enabled Boolean True (default): Enables the XPInstall system (i.e., allows extensions to be installed)
False: Opposite of the above
Note: In Firefox 1.0.x, this can be changed in "Tools → Options → Web Features → Allow web sites to install software" (UI removed in Firefox 1.5).
xpinstall. whitelist. add String A comma-separated list of sites to automatically add to the extensions whitelist. Default value is update.mozilla.org,addons.mozilla.org but is cleared as soon as the values are added to the whitelist
xpinstall. whitelist. required Boolean True (default): When installing extensions from remote hosts, remote host must be on the whitelist
False: Opposite of the above

Miscellaneous preferences

See Mail and news settings for other miscellaneous preferences related to Thunderbird and Mozilla Suite/SeaMonkey mail and news.

Name Type Meaning of Values
allinonegest. * Varied These preferences are set via the All in One Mouse Gestures extension.
application. use_ns_plugin_finder Boolean True: When a plugin is not found, clicking on the puzzle piece will open a dialog telling the user what plugin is needed. Clicking on the "Get the Plugin" button brings the user to the plugins installation page.
False (default): Clicking on the puzzle piece will send the user to that plugin's page on plugins.netscape.com which will have a link to that plugin's installation page.
backups. number_of_prefs_copies Integer Unused (obsolete). Previously: number of backup copies of prefs.js to keep.
clipboard. autocopy Boolean True: Selecting text automatically copies it to the clipboard
False (default): Opposite of the above
Note: *nix only.
converter. html2txt. header_strategy Integer How to format HTML headers (H1-H6) when saving a web page as text-only
0: No indentation
1 (default): Indent headers based on header level (i.e. H(n+1) is indented more than H(n))
2: Number headings and indent slightly
converter. html2txt. structs Boolean Determines whether to format "structured" elements (<strong>, <em>, <code>, <sub>, <sup>, <b>, <i>, <u>) with other characters when saving a web page as text-only
True (default): *Strong*, /em/, |code|, _sub, ^sup, *b*, /i/, _u_
False: Strong, em, code, sub, sup, b, i, u
custtoolbar. personal_toolbar_folder String Custom name for the Personal Toolbar Folder. If empty (default), name is determined by string bundle or the hard-coded value "Personal Toolbar Folder".
gfx. color_management. display_profile String Full path to an ICM profile for output. Default is an empty string in which case the systems global profile is used. If no global profile can be found a default sRGB profile is used.
gfx. color_management. enabled Boolean True: Enable color management for rendered graphics.
False (default): Disable color management.
Obsolete since 2008. See gfx.color_management.mode below.
gfx. color_management. mode Integer When to use color management for graphics:
0: Never
1: Always
2: Only for tagged images (default)
gfx. use_text_smoothing_setting Boolean True:
False (default): .
image. animation_mode String Determines how to animate multi-frame GIF images
none: animated images will never play.
once: animated images will play once.
normal (default): animated images will play as normal.
images. dither String Whether to dither images
auto (default): Automatically decide
true: Dither images
false: Disable image dithering
ime. password. onBlur. dontCare Boolean Determines how an IME editor window should react when password fields lose focus (see bug 16940).
True: Leave the IME open
False (default): Re-open the IME if it was open prior to the password field's focus.
Note: Firefox 1.5 and above only.
ime. password. onFocus. dontCare Boolean Determines how an IME editor window should react when password fields gain focus (see bug 16940).
True: Leave the IME open
False (default): Close the IME.
Note: Firefox 1.5 and above only.
inspector. * Varied These entries apply to the DOM Inspector and are only relevant if you have it installed.
keyword. URL String URL to use for keyword lookups. Default value in Firefox 2.0 is

http://www.google.com/search? ie=UTF-8&oe=UTF-8&sourceid=navclient&gfns=1&q=

keyword. enabled Boolean Determines whether to use keywords
True (default): Send non-URLs entered in the Location Bar to the URL specified in keyword.URL
False: Disable keywords
mail. ui. display. dateformat. today Integer See Change the Date Format.
permissions. default. image Integer Determines when images should be loaded.
1 (default): Load all images
2: Do not load any images
3: Load images from same (originating) server only
Note: This preference was previously known as network.image.imageBehavior prior to Firefox 1.5.
pfs. datasource. url String Determines where the plugin finder service should query for plugin information. Default value is pulled from chrome://mozapps/locale/plugins/plugins.properties
places. frecency. * Integer These prefs are used for the frecency calculation process.
prefs. converted-to-utf8 Boolean True: The preferences have been converted to UTF-8; decode as appropriate
False (default): Opposite of the above
roaming. default. files String A comma-separated list of files that will be selected for roaming by default. Default value is bookmarks.html,abook.mab,cookies.txt.
roaming. showInitialWarning Boolean True (default): Display a general warning to the user about making backups, security, etc.
False: Opposite of the above
signed. applets. codebase_principal_support Boolean True: Give scripts using codebase principals access advanced scripting capabilities. Setting this preference to "true" is often used to allow IRC websites to gain access to the OS's clipboard at the expense of a security risk.
False (default): Only trusted/signed scripts can access advanced scripting capabilities
Note: file: and resource: schemes are considered "special" and may get extra capabilities regardless of this preference's setting.
slider. snapMultiplier Integer Determines the size of the scrollbar snapping region. Default value is 6 in Windows; 0 (disabled) in *nix.
startup . homepage_override_url String The URL that Firefox goes to when the user starts up the browser after upgrading. In Firefox, defaults to
http://%LOCALE%.www.mozilla.com/ %LOCALE%/%APP%/%VERSION%/whatsnew/.
startup. homepage_welcome_url String The URL that Firefox goes to when the user starts up the browser after the initial installation, or with a new profile. In Firefox, defaults to
http://%LOCALE%.www.mozilla.com/ %LOCALE%/%APP%/%VERSION%/firstrun/.
svg. enabled Boolean True (default): On SVG-enabled builds, enables internal SVG renderer, disables externals
False: Opposite of the above (see bug 258511)
urlclassifier. keyupdatetime. * Integer Time stamps used by Safe Browsing in Firefox to record the latest updates downloaded and stored in urlclassifier2.sqlite. Downloading is controlled by browser.safebrowsing.remoteLookups.
See Phishing Protection in the Mozilla Wiki.
urlclassifier. tableversion. * String Version numbers used by Safe Browsing in Firefox to record the latest updates downloaded.
viewmanager. do_doublebuffering Boolean Determines whether the viewmanager should do double-buffering by default (see bug 169483).
wallet. caveat Boolean Marks whether the user has been shown the warning message regarding security risks of using the Wallet feature.
wallet. crypto. autocompleteoverride Boolean Indicates whether browser should ignore the autocomplete="off" attribute in forms.}