About:config entries

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Revision as of 05:43, 27 February 2005 by Unarmed (talk | contribs) (Added: browser.cache.memory.capacity; formatting tweaks; added some Bugzilla refs)
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about:config is a list of preferences that you can change. This article is meant to be a partial documentation of those preferences. Alternative list can be found here [1].

See also: Editing configuration and User.js file.

Many of the entries that appear in Firefox will also apply to Mozilla and vice versa.

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

Accessibility.*

Name Type Meaning of Values
accessibility. accesskeycausesactivation Boolean True: Using an accesskey will have the same effect as clicking on the applicable element with the mouse.

False: Using an accesskey will only focus the applicable element.

accessibility. browsewithcaret Boolean True: A caret is present in the browser window to use to select text with the keyboard.

False: No caret is present.
This can be toggled using the [F7] key.

accessibility. tabfocus Integer Determines which web page elements can gain focus when [Tab] key is pressed.

1: Text field form controls only
2: All form controls except text fields
3: All form controls
4: Hyperlinks and hyperlinked images
7: All form controls and hyperlinks

accessibility. typeaheadfind Boolean True: Activates Find As You Type.

False: Disables Find As You Type.
Note: in Firefox, this can be changed via Tools → Options → Advanced → Accessibility → Begin finding when you begin typing

accessibility. typeaheadfind. autostart Boolean True: Find As You Type will start automatically when typing starts and a form control like a text area or text box does not have focus.

False: Find As You Type will only start when / is pressed for any word and when ' is pressed for link searching.

accessibility. typeaheadfind. enablesound Boolean True: Find As You Type will play a sound when the typed in search phrase is not found.

False: Find As You Type will not play any sounds.

accessibility. typeaheadfind. enabletimeout Boolean True: Find As You Type will end after a set time if no keys are pressed.

False: Find As You Type will not end due to a timeout. To end a search use the escape key.

accessibility. typeaheadfind. flashBar Integer 0: Don't flash the Find Toolbar when a result is found

1: Flash the Find Toolbar's search field when a result is found
Note: As of 1.0, this feature is sketchy at best and nonfunctional at worst.

accessibility. typeaheadfind. linksonly Boolean True: Find As You Type will only search links.

False: Find As You Type will search all the text.

accessibility. typeaheadfind. soundURL String Specify filename (.wav) for the error sound, or use "default" for default sound or "beep" for system beep.
accessibility. typeaheadfind. startlinksonly Boolean True: When finding links, the search will only match links from the beginning of the link's text.

False: The search will match any part of a link's text.

accessibility. typeaheadfind. timeout Integer The number of milliseconds that Find As You Type will wait between key presses before ending an active search.
accessibility. usebrailledisplay String Specifies the Braille display module to use

Note: Currently unused. Planned for future use.

accessibility. usetexttospeech String Specifies the text-to-speech module to use with the browser (e.g. "ViaVoice")

Note: Currently broken.

accessibility. warn_on_browsewithcaret Boolean True: You will be promted to comfirm enabling caret browsing.

False: The opposite of above.

Advanced.*

Name Type Meaning of Values
advanced. always_load_images Boolean Unused. Holdover from Netscape 4.x (then general.always_load_images).
advanced. mailftp Boolean True: Use a specified email address (the value in network.ftp.anonymous_password) as the password for anonymous FTP servers

False: Send default "mozilla@example.com" for password

advanced. system. supportDDEExec Boolean Previously (before 0.9) used to open links from external sources as tabs in a single window. Currently deprecated in favor of preferences under Tools → Options → Advanced → Tabbed Browsing.

Alerts.*

Note: These apply to the "Downloads Complete"- and "Updates Available"-style alerts, not regular JavaScript alert() dialogs.

Name Type Meaning of Values
alerts. height Integer Height in pixels of the alert box
alerts. slideIncrement Integer How many pixels to move per step when "sliding"
alerts. slideIncrementTime Integer How many miliseconds per step of "slide" movement
alerts. totalOpenTime Integer How many miliseconds to show the alert

App.*

Name Type Meaning of Values
app. build_id String Date of build in YYYYMMDD format
app. extensions. version String Browser version given to extensions to check for compatibility
app. id String The GUID corresponding to the program ({ec8030f7-c20a-464f-9b0e-13a3a9e97384} in the case of Firefox)
app. update. autoUpdateEnabled Boolean True: Periodically check update.mozilla.org in the background for updates to the browser

False: Disable all checks for browser updates
Note: In Firefox, this can be changed via Tools → Options → Advanced → Software Update → Periodically check for updates to Firefox

app. update. enabled Boolean True: Allow updates to the browser

False: Disable browser updates
Note: Probably deprecated in favor of app.update.autoUpdateEnabled

app. update. interval Integer Number of seconds between checks for updates (by default, 1000 days)
app. update. lastUpdateDate Integer Time of last update in UNIX epoch format (seconds since 1970-01-01)
app. update. performed Boolean True: Browser updates have been installed

False: No browser update has been performed

app. update. updatesAvailable Boolean True: The update manager has found updates

False: There are no updates to download or install

app. update. url String URL for browser update notification
app. version String Version number

Bidi.*

Name Type Meaning of Values
bidi. browser. ui Boolean True: Allows the browser interface to use a bi-directional language set

False: Opposite of the above

bidi. characterset Integer How the browser determines the character set to use

1: Document-specified character set
2: Default character set

bidi. controlstextmode Integer How controls are used

1: Logical
2: Visual
3: Container

bidi. direction Integer Select direction of text

1: Left-to-right
2: Right-to-left

bidi. numeral Integer How numerals are displayed

1: Regular context numerals
2: Hindi context numerals
3: Arabic numerals
4: Hindi numerals

bidi. support Integer Select provider of bi-directional support

1: Mozilla
2: OS
3: Disable

bidi. texttype Integer Type of text

1: Charset
2: Logical
3: Visual

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: In Firefox, this can be changed via "Tools → Options → General → Fonts & Colors → Unvisited Links".
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.
browser. bookmarks. file String The full path and filename of your bookmarks file (bookmarks.html).
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. 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 → 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 → Manage Bookmarks... → View"
browser. cache. check_doc_frequency Integer 0: Check the cached page is current 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 → Privacy → 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_cache_ssl Boolean True: Cache content received via SSL (security risk!)
False (default): Do not cache content received via SSL
Note: More information in Bug 205921
browser. cache. memory. capacity Integer Amount of RAM allowed for the browser's cache (in KB). Not set by default to allow automatic sizing of capacity. Setting a value overrides the automatic sizing; setting to 0 disables the memory cache device entirely.
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

--OR--
browser. chrome. site_icons

Boolean True (default): favicons/site icons will be visible, cached, etc.
False: favicons/site icons will be not visibile, cached, etc.
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 explicity set, and XUL error pages. Default value is #FFFFFF.
Note: In Firefox, this can be changed via "Tools → Options → General → Fonts & Colors"
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): Opposite of above Note: This appears to happen in Firefox regardless of this setting
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 → General → Fonts & Colors"
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 DPI of display device. Affects CSS absolute length units (e.g. pt, mm).
-1: Unable to determine the resolution (assume preference is not set)
0: Force use of operating system's logical resolution
(n): Assume screen DPI of n. Default value is 96.
Note: In Firefox, this can be changed via "Tools → Options → General → Fonts & Colors → Display Resolution"
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 → General → Fonts & Colors → Always use my colors"
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 → General → Fonts & Colors → Always use my 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 → General → Fonts & Colors → Use system colors"
browser. dom. window. dump. enabled Boolean True: Enable JavaScript dump() output
False: Opposite of the above
browser. download. dir String The last directory used for saving a file from the "What should (browser) do with this file?" dialog.
browser. download. folderList Integer Which of several internally-specified locations to use for the default download directory
0 (default): the desktop
1: the downloads folder
2: the last folder specified for a download
Note: In Firefox, this can be changed via "Tools → Options → Downloads → Download Folder → Save all files to this folder"
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 → Downloads → Download Manager → Close the Download Manager when all downloads are complete"
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 miliseconds 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 → Download Manager History"
browser. download. manager. showAlertInterval Integer Number of miliseconds 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. 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 → Downloads → Download Manager → Show Download Manager window when a download begins"
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
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. 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 → Downloads → Download Folder → Ask me where to save every file"
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 → Multimedia → Resize large images to fit in the browser window"
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. 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 → Saved Form Information → Save information I enter in web page forms and the Search Bar"
browser. forms. submit. backwards_compatible Boolean True (default): Leave off mandatory Content-Transfer-Encoding header when doing form submits
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. 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. 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. 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 days to remember visited pages in history. Default value is 9.
Note: In Firefox, this can be changed via "Tools → Options → Privacy → History → Remember visited pages for the last ___ days"
browser. link. open_external Integer Where to open links sent to the browser from an external application
2: Opens external links in a new window
3: Opens external links in a new tab
1 (or anything else) (default): Opens external links in current window
Note: In Firefox, this can be changed via "Tools → Options → Advanced → Tabbed Browsing → Open links from other applications in:"
browser. link. open_newwindow Integer Where to open links that would normally open in a new window
2 (default): In a new window
3: In a new tab
1 (or anything else): In the current window
browser. link. open_newwindow. restriction Integer Firefox only. Source: The Burning Edge.
0 (default): 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: 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. 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. 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. animateFadeIn Boolean True (default on all platforms but Mac): When switching prefs panels, change the height of the window and fade the new panel in over about a second.
False: Do not animate switching pref panels
Note: This feature is only available in the Firefox trunk builds (1.1)
browser. preferences. instantApply Boolean True (default on 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.
Note: This feature is only available in the Firefox trunk builds (1.1)
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. 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. 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. order. (number) String (number) is a digit 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 weighting search engine entry sorting. Points to .properties file.
browser. search. selectedEngine String Name of currently selected search engine plugin
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. shell. checkDefaultBrowser Boolean Check the OS' 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 → General → Default Browser"
browser. startup. homepage String URL of homepage, or pipe (|)-separated list of URLs to open in tabs when going to the homepage
Note: In Firefox, this can be changed via "Tools → Options → General → 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 (probably does not work)
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 → Advanced → Tabbed Browsing → Hide the tab bar when only one web site is open"
browser. tabs. forceHide Boolean Display of the tab bar
True: Hide the tab bar regardless of number of tabs
False (default): Show tab bar normally
browser. tabs. loadBookmarksInBackground Boolean 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: In Firefox, this can be changed via "Tools → Options → Advanced → Tabbed Browsing → Select New Tabs from Bookmarks or History"
browser. tabs. loadDivertedInBackground Boolean True: Any page that is supposed to open in a new window (target="_new" or from an external program) that instead gets diverted into a new tab will load in the background.
False (default): Any page that is supposed to open in a new window (target="_new" or from an external program) that instead gets diverted into a new tab will load in the foreground taking the focus from the current tab.
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.
browser. tabs. loadGroup Integer 0: Append group to current tab set
1 (default): Replace current tab set with group
Note: This appears to be deprecated in favor of browser.tabs.loadFolderAndReplace
browser. tabs. loadInBackground Boolean Focus behavior for new tabs
True (default): Focus new tabs opened from links (bring to foreground)
False: Opposite of above
Note: In Firefox, this can be changed via "Tools → Options → Advanced → Tabbed Browsing → Select new tabs opened from links"
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
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. urlbar Boolean Determines the behavior of pressing Enter in the address bar or clicking the Go button. Does not currently work.
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. (See Bug 266759.)
True: Show "Force links that open in new windows to open in..." options under "Tools → Options → Advanced → Tabbed Browsing"
False (default): Opposite of above
browser. tabs. warnOnClose Boolean True (default): The broswer 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 thanone tab.
Note: In Firefox, this can be changed via "Tools → Options → Advanced → Tabbed Browsing → Warn when closing multiple tabs"
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 Seemingly nothing. (Never referenced in code.)
browser. turbo. enabled Boolean 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
Note: Pref removed (obsolete).
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 → General → 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. clickSelectsAll Boolean True (default): Select the contents of the address bar when it is clicked
False: Opposite of above
browser. urlbar. matchOnlyTyped Boolean Determines behavior of autocomplete in Location bar

True: Only matches typing against URLs specifically typed into Location bar
False (default): Match against history

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 → General → 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: The browser will use error pages.
False (default): The browser will use error alert boxes.

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 fo above
Note: In Firefox, this can be changed via Tools → Options → Web Features → Enable JavaScript / Advanced → Allow scripts to change images
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 miliseconds), handle the popup according to the current popup blocker settings. Default is 1000.
dom. disable_open_during_load Boolean Determines popup blocker behavior
True (default): Block popup windows created while the page is loading
False: Allow popup windows
Note: In Firefox, this can be changed via Tools → Options → Web Features → Block Popup Windows
dom. disable_window_flip Boolean Determines whether windows can be focus()ed via non-chrome JavaScript.
True: Windows may not be set as active via JavaScript
False (default): Opposite of the above
Note: In Firefox, this can be changed via Tools → Options → Web Features → Enable JavaScript / Advanced → 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: Windows may not be moved or resized via JavaScript
False (default): Opposite of the above
Note: In Firefox, this can be changed via Tools → Options → Web Features → Enable JavaScript / Advanced → Allow scripts to move or resize existing windows
dom. disable_window_open_feature. * Boolean Web Page 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): JavaScript access to window.status is disabled
False: Opposite of the above
Note: In Firefox, this can be changed via Tools → Options → Web Features → Enable JavaScript / Advanced → 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 → Web Features → Advanced → Allow scripts to disable or replace context menus
dom. max_script_run_time Integer Determines the maximum amount of time in seconds a script can run. Default is 5. Negative values are ignored and 5 seconds is used instead.
dom. popup_allowed_events String A space-separated list of the events that are allowed to create popups. By default, "change click dblclick mouseup reset submit".
dom. popup_maximum Integer The maximum number of simultaneously open popup windows. Default is 20.

Editor.*

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

Name Type Meaning of Values
editor. css. default_length_unit String Determines the default units for CSS rules.
cm: centimeters
em: ems (width of the capital letter "M")
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. The default is 72.
editor. positioning. offset Integer The default offset, both X and Y, of absolutely positioned elements. The default 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: Paste content intact (include newlines)
1 (default): 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
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.
True: Use colors specified in editor.* preferences for content
False (default): Use the default colors

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 String The default generic-family to use.
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

Middlemouse.*

Name Type Meaning of Values
middlemouse.contentLoadURL Boolean By default, this is true on Linux and false on all other OSes. If this is set to true, it will override middle-clicking tabs to close them.
True: Firefox will go to whatever is currently in your clipboard.
False: Firefox will never do the aforementioned when you middle click.
middlemouse.openNewWindow Boolean No effect in Firefox. In Mozilla, if browser.tabs.opentabfor.middleclick is false and this is true, middle-clicking a link will open it in a new window.
middlemouse.paste Boolean By default, this is true on Linux and false on all other OSes. This only applies when you have focus is a text field or area.
True: Middle-clicking a text field or area will paste whatever is in your clipboard into the text field or area.
False: It will not.

Mousewheel.*

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

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

Type is then one of:

action
integer value that determines the type of action:
0
  • Scroll document by X lines
  • 1 : Scroll document by one page
  • 2 : Move back/forward in history
  • 3 : Make text larger/smaller
numlines
number of lines to scroll by (if relevant)
sysnumlines
use system preferences to determine how many lines to scroll by

Network.*

Name Type Meaning of Values
network.dns.ipv4OnlyDomains String A comma-separated list of domains for which DNS lookups are for IPv4 addresses only. (Default value is ".doubleclick.net". More info at Bug 68796.)
network.http.redirection-limit Integer This number will limit how many consecutive HTTP redirects Firefox can do. The default number is "20". Setting it to "0" will stop all redirects from occuring.

Miscellaneous

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: 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.
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
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".
extension. * Varied These entries are added by extensions. Most extension preferences can be edited using that extension's options dialog. Extension option dialogs are accessed using the extension manger. Not all extension options start with the extension keyword.
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.
layout. frames. force_resizability Boolean Determines whether frame noresize attribute is honored.
True: All frames will be resizable, resulting in a movable separator between frames.
False (default): The resizability of frames is determined by the web page.
mail. ui. display. dateformat.today Integer See Change the Date Format.
mail. ui. display. dateformat.today Integer See Change the Date Format.
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: blocks popups from plugins
3: blocks them even on whitelisted sites.
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 using View → Wrap Long Lines in the view source window.