About:config entries

about:config is a list of preferences that you can change. This article is meant to be a partial documentation of those preferences. Alternative lists can be found here [1], here [2] and here [3].

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 (default): 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 (default): 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 (default): All form controls and hyperlinks
accessibility. typeaheadfind	Boolean	True: Activates Find As You Type. False (default): 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 (default): 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 (default): 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 (default): 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 Firefox 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 (default): Find As You Type will search all the text.
accessibility. typeaheadfind. soundURL	String	The sound to play when Find As You Type does not find a match. (filename): .wav file to play for the error sound default (default): The default sound beep: 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 (default): 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. Default value is 5000.
accessibility. usebrailledisplay	String	Specifies the Braille display module to use. Default value is an empty string. Note: Currently unused. Planned for future use.
accessibility. usetexttospeech	String	Specifies the text-to-speech module to use with the browser (e.g. "ViaVoice"). Default value is an empty string. Note: Currently broken.
accessibility. warn_on_browsewithcaret	Boolean	True (default): 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). Default value is true.
advanced. mailftp	Boolean	True: Use a specified email address (the value in network.ftp.anonymous_password) as the password for anonymous FTP servers False (default): Send default "mozilla@example.com" for password
advanced. system. supportDDEExec	Boolean	Previously used (before Firefox 0.9) to open links from external sources as tabs in a single window. Currently deprecated in favor of preferences under "Tools → Options → Advanced → Tabbed Browsing". Default value is true.

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. Default value is 50.
alerts. slideIncrement	Integer	How many pixels to move per step when "sliding". Default value is '1.
alerts. slideIncrementTime	Integer	How many milliseconds per step of "slide" movement. Default value is 10.
alerts. totalOpenTime	Integer	How many milliseconds to show the alert. Default value is 4000.

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. Default value for Firefox is {ec8030f7-c20a-464f-9b0e-13a3a9e97384}.
app. update. autoUpdateEnabled	Boolean	True (default): 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 (default): 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. Default value is 86400000 (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 (default): No browser update has been performed
app. update. updatesAvailable	Boolean	True: The update manager has found updates False (default): There are no updates to download or install
app. update. url	String	URL for browser update notification. Default value is https://update.mozilla.org/update/firefox/en-US.rdf.
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 (false): Opposite of the above
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 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

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). In Windows, the path separator must be two slashes (e.g. "C:\\Path\\To\\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	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 → 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. parent_directory	String	Full path to the directory used for storing the browser's cache. In Windows, the path separator must be two slashes (e.g. "C:\\Path\\To\\Cache")
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	Determines how the browser uses RAM for cache. -1 (default): Automatically set size of capacity as a percentage of physicall 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 --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 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 → Download Manager History"
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. 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 Note: Does not work in Firefox 1.0 (See Bug 269664)
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 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): 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 value 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. Default value is "change click dblclick mouseup reset submit".
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). 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. 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: 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

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: Opposite of the above Note: In Firefox, this can be changed via "Tools → Options → Advanced → Browsing → Use autoscrolling"
general. config. obscure_value	Integer	An integer to use when obscuring the preferences file saved to and read from disk. Default value is 13 (effectively, ROT-13 the content).
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 → Themes"
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 → Browsing → Use smooth scrolling"
general. startup. browser	Boolean	True (default): When launching Mozilla, 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.
general. useragent. contentlocale	String	The content locale ISO 639-2 value specified in the User-Agent string
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).
general. useragent. vendorSub	String	Vendor substring in the User-Agent string. Default value depends on browser version (1.0 in Firefox 1.0)

Intl.*

Name	Type	Meaning of Values
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. locale. matchOS	Boolean	Determines how to decide locale True: Use the locale the OS is using False (default): Opposite of the above
intl. menuitems. alwaysappendaccesskeys	String	Specifies URI to determine if access keys are appended to menu items

Javascript.*

Name	Type	Meaning of Values
javascript. allow. mailnews	Boolean	Determines whether Javascript can be executed in Mozilla Mail/News. True: Enable Javascript False (default): Disable Javascript
javascript. enabled	Boolean	Determines whether Javascript can be executed in the browser. True (default): Enable Javascript False: Disable Javascript Note: In Firefox, this can be changed via "Tools → Options → Web Features → Enable JavaScript"
javascript. options. showInConsole	Boolean	Determines whether chrome errors should be displayed in the JavaScript Console. True: Show chrome errors in the console False (default): hide errors
javascript. options. strict	Boolean	Determines whether to enable strict Javascript warnings in the JavaScript Console. True: Enable strict Javascript error reporting False (default): Opposite of the above

Layout.*

Name	Type	Meaning of Values
layout. enable_japanese_specific_transform	Boolean	Determines whether or not to replace backslashes with Yen signs in documents encoded in one of Japanese legacy encodings (EUC-JP, Shift_JIS, ISO-2022-JP) True: Replace backslashes False (default): Opposite of the above
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.
layout. word_select. eat_space_to_next_word	Boolean	Determines whitespace selection behavior when double-clicking a word True (default): Select the space up to but not including the next word along with the word False: Just select the word with no extra whitespace
layout. word_select. stop_at_punctuation	Booelan	Determines punctuation selection behavior when double-clicking a word True (default): Don't select punctuation automatically with the word False: Select the punctuation as well as the word

Middlemouse.*

Name	Type	Meaning of Values
middlemouse. contentLoadURL	Boolean	Determines how to handle middle-clicks in the content area. True (default in Linux): Go to whatever address is currently in the clipboard False (default in all but Linux): Handle middle-clicks normally. Note: No effect in Firefox
middlemouse. openNewWindow	Boolean	Determines behavior of middlemouse.contentLoadURL when that preference is true. True (default): Open links that are middle-clicked in a new window False: Opposite of the above. Note: No effect in Firefox.
middlemouse. paste	Boolean	Determines behavior of middle-clicks when text fields or text areas have focus. True (default in Linux): Middle-clicking a text field or area will paste whatever is in your clipboard into the text field or area. False (default in all but Linux): Opposite of the above
middlemouse. scrollbarPosition	Boolean	Determines behavior of middle-clicks in the scrollbar. True (default in Linux): Center the scroll position on the scrollbar at the coordinates of the middle-click False (default in all but Linux): Don't move the scroll position on middle-click

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. autodial-helper. enabled	Boolean	Help Windows NT, 2000, and XP dialup a RAS connection when a network address is unreachable. True: Launch dialer when address is unreachable False (default): 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). True: Always accept session cookies False (default): Apply current cookie policy to session cookies
network. cookie. cookieBehavior	Integer	Determines how the browser should handle cookies. 0 (default): Enable all cookies 1: Allow cookies from originating server only 2: Disable all cookies 3: Use P3P policy to decide Note: In Firefox, this can be changed via "Tools → Options → Privacy → Cookies → Allow sites to set cookies / for the originating web site only"
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
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 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
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)
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)
network. dns. disableIPv6	Boolean	Determines whether to perform IPv6 name lookups (See Bug 68796) True: Do not perform lookups False (default): Opposite of the above
network. dns. ipv4OnlyDomains	String	A comma-separated list of domains for which DNS lookups are for IPv4 addresses only. Default value is .doubleclick.net. (See Bug 68796.)
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 if advanced.mailftp is true instead of simply "mozilla@example.com". 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.
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. Seems to be unused.
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 24.
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 8.
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 4.
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 2.
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. maxrequests	Integer	Determines the maximum number of HTTP requests in the pipeline (sent sequentially without waiting for a response). 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. Appears to be unused. 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. 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"
network. image. warnAboutImages	Boolean	Determines whether to prompt the user before loading an image. True: Load no images until user confirms False (default): Load images normally Note: Pref unused (feature disabled). See Bug 146513.
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. 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. 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. 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

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 (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.
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.
images. dither	String	Whether to dither images auto (default): Automatically decide true: Dither images false: Disable image dithering
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 is http://www.google.com/search?btnI=I%27m+Feeling+Lucky&ie=UTF-8&oe=UTF-8&q= in Firefox 1.0.
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.
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.