About: Configuration Entries

About:config entries
The correct title of this article isabout:config entries. It appears incorrectly here due to technical limitationsin the wiki software.
This is not the place to edit your configuration settings.This is a reference to the entries in about:config, where all user preferences can be viewed and modified. In most cases the list below doesn't state whether a given preference applies to all, or only some (and which), of Firefox, Thunderbird, Mozilla Suite, SeaMonkey, or even the now discontinued Sunbird: trial and error is often the only way to tell if some particular preference applies toyourversion ofyourapplication.
Users not already familiarwithabout:config entriesshould read thecompanion article, about:config, which describeshow to modifyvalues and work with theabout:configlist.
This article does not contain a complete list of all preferences.If you don't find an entry below for a given preference, check the Category:Preferences(multiple-page) listing, which includes many new preferences that have not been added here, as well as those preferences that have been migrated from sections of this article. Also check Mail and news settingsfor a listing of Thunderbird and Mozilla Suite/SeaMonkey mail and news preferences. Alternative lists can be found here:
. the Preferential project
. Mozilla's embedding documentation
. Preferences - MDN
. Mozilla Preference reference - MDN
. Mozilla Networking Preferences - MDN
(For a comparison view of table and actual about:config settings, use the Fox Splitter (formerly Split Browser)extension or the new version of Fox-Splitterto show one above the other. Also, finding item documentation for a preference from within about:configcan be sped up with the Prefsearchextension, which adds a context menu item to search Google for the selected preference item.)
Note:There is no indication in the table as to which items will take effect immediately, with a new window, or require restarting.
Spaces between the dots in preference names on this page exist purely for word-wrapping.They are actually not present and should not be thought as so. Editors of this page must take care to follow this convention in order to not force users to horizontally scroll this article.
Contents[ hide]
1 Accessibility.
2 Advanced.
3 Alerts.
4 App.
5 Bidi.
6 Browser.
7 Config.
8 Content.
9 DOM.
10 Editor.
11 Extensions.
12 Font.
13 Geo.
14 General.
15 Intl.
16 Javascript.
17 Layout.
18 Mail.
19 Mailnews.
20 Middlemouse.
21 Mousewheel.
22 Network.
23 News.
24 NGLayout.
25 Plugin.
26 Print.
27 Privacy.
28 Profile.
29 Security.
30 Signon.
31 Snav.
32 Toolkit.
33 UI.
34 Update. and Update_notifications.
35 View_source.
36 XPInstall.
37 Miscellaneous preferences[ edit]
Accessibility.
accessibility. allows you to modify Find As You Type behavior, change how the [Tab] key works in web pages and XUL, turn on caret browsing, and tweak other accessibility-related features.
accessibility. has been migrated to Category:Preferences.[ edit]
Advanced.
advanced contains two prefs: Advanced.mailftpand Advanced.system.supportDDEExec.
advanced. has been migrated to Category:Preferences.[ edit]
Alerts.
alerts. contains three prefs, all related to the GUI: Alerts.slideIncrement, Alerts.slideIncrementTime, and Alerts.totalOpenTime.
alerts. has been migrated to Category:Preferences.[ edit]
App.
app. allows you to modify application update behaviour.
app.* has been migrated to Category:Preferences.[ edit]
Bidi.
NameTypeMeaning of Values
bidi. browser. uiBooleanTrue: Activates bidi interface and keyboard unconditionally
False: Only activates bidi interface and keyboard in bidi locales. (Default)
bidi. charactersetIntegerHow the browser determines the character set to use
1(default): Document-specified character set
2: Default character set
bidi. controlstextmodeIntegerHow controls are used
1(default): Logical
2: Visual (this is no longer supported and leads to strange side-effects, see bug 373319)
3: Container
bidi. directionIntegerSelect direction of text
1(default): Left-to-right
2: Right-to-left
bidi. numeralIntegerHow numerals are displayed
0(default): Nominal numerals
1: Regular context numerals
2: Hindi context numerals
3: Arabic numerals
4: Hindi numerals
bidi. supportIntegerSelect provider of bi-directional support
1(default): Mozilla
2: OS
3: Disable
bidi. texttypeIntegerType of text
1(default): Charset
2: Logical
3: Visual
bidi.edit.caret movement style
bidi.edit.delete immediately[ edit]
Browser.
NameTypeMeaning of Values
browser. active_colorStringThe default color for active links as a hex code. Default is#EE0000.
browser. anchor_colorStringThe default color for links as a hex code. Default is#0000EE
Note: This can be changed in Firefox via " Tools → Options→ Content / Fonts & Colors → Colors... → Link Colors → Unvisited Links" (Firefox 1.5 and above) and via "Edit → Preferences → Appearance → Colors / Link Colors → Unvisited Links" in Mozilla Suite and SeaMonkey.
browser. backspace_actionIntegerDetermines the behavior of the backspace key
0: Goes back in history
1: Acts as Page Up
2(and above): Does nothing
Note: See bug 301248(Mozilla Suite)
browser. blink_allowedBooleanTrue(default): Use of the blink tag or CSS's text-decoration: blinkwill result in blinking elements.
False: Blinking is disabled.
browser. block. target_new_windowBooleanTrue: Links with target set to_blankwill open in the current tab instead of a new window.
False: Links with target set to_blankwill open in a new window.
Note: No longer in use. Usebrowser.link.open_newwindowinstead.
browser. bookmarks. added_static_rootBooleanKeeps track of whether a root folder for system (imported) bookmarks has been created inbookmarks.html.
True: The root folder has been created
False(default until import complete): Create the root folder (unless we're using dynamic bookmarks -browser.bookmarks.import_system_favorites), and then set this pref to true.
browser. bookmarks. fileStringThe full path and filename of your bookmarks file (bookmarks.html). In Windows, the path separator must be two backslashes (e.g. "C:\Path\To\bookmarks.html") if the value is being set inuser.jsorprefs.jsinstead of withinabout:config
browser. bookmarks. import_system_favoritesBooleanDetermine 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_secondsIntegerThe number of seconds between Live Bookmark checks. Values under 60 are assumed to be 60; the default is3600(1 hour).
browser. bookmarks. restore_default_bookmarksBooleanTrue: Overwrite the current bookmarks.htmlfile with the default set of bookmarks.
False(default): Do not reset bookmarks.
Note: Firefox 1.5 and above only
browser. bookmarks. sort. directionStringThe order in which to sort bookmarks in the Bookmarks Manager
descending(default): Unsorted
natural: Alphabetically, A-Z
ascending: Alphabetically, Z-A
Note: In Firefox, this can be changed via "Bookmarks → Organize (or Manage) Bookmarks... → View"
browser. bookmarks. sort. resourceStringThe RDF source to use when sorting the bookmarks in the Bookmarks Manager
rdf: http://home.netscape.com/NC-rdf#Name(default) - by bookmark name
rdf: http://home.netscape.com/NC-rdf#URL- by URL
rdf: http://home.netscape.com /NC-rdf#ShortcutURL- by bookmark keyword
rdf: http://home.netscape.com /NC-rdf#Description- by description
rdf: http://home.netscape.com /NC-rdf#BookmarkAddDate- by bookmark creation date
rdf: http://home.netscape.com /WEB-rdf#LastModifiedDate- by bookmark modification date
rdf: http://home.netscape.com /WEB-rdf#LastVisitDate- by date of last visit
Note: In Firefox, this can be changed via "Bookmarks → Organize (or Manage) Bookmarks... → View"
browser. cache. check_doc_frequencyIntegerHow 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. capacityIntegerAmount of disk space allowed for the browser's cache (in KB). Default is50000.
Note: In Firefox, this can be changed via " Tools → Options→ Advanced → Network / Offline Storage" (Firefox3), Tools → Options → Advanced → Network / Cache" (Firefox 2) or "Tools → Options → Privacy → Cache (Firefox 1.5 and earlier); in Mozilla Suite/SeaMonkey, via " Edit → Preferences→ Advanced → Cache".
browser. cache. disk. enableBooleanTrue(default): Use disk cache, up to capacity specified inbrowser.cache.disk.capacity
False: Disable disk cache (same effect as settingbrowser.cache.disk.capacityto 0)
browser. cache. disk. parent_directoryStringFull path to theparentdirectory of theCachefolder used for storing the browser's cache. In Windows, the path separator must be two backslashes (e.g. "C:\Path\To\Parent\Folder") if the value is being set in theuser.jsorprefs.jsinstead of withinabout:config.
browser. cache. disk_cache_sslBooleanTrue(default): Cache content received via SSL
False: Do not cache content received via SSL
Note: See bug 531801for more information
browser. cache. memory. capacityIntegerDetermines how the browser uses RAM for cache.
-1(default): Automatically set size of capacityas a percentage of physical RAM
0: disables the memory cache device entirely
(n): Set the maximum RAM used tonKB.
browser. cache. memory. enableBooleanTrue(default): Use memory cache, up to capacity specified inbrowser.cache.memory.capacity(if set); otherwise, use a percentage of physical RAM (see bug 105344)
False: Disable memory cache (same effect as settingbrowser.cache.memory.capacityto 0)
browser. chrome. faviconsBooleanTrue(default): Load and display "favicons" residing in the current page's site root directory
False: Opposite of the above
Note: This should be set to the same value asbrowser.chrome.site_iconsfor legacy reasons.
browser. chrome. image_icons. max_sizeIntegerIf an image's height or width is greater than this number (in pixels), the image will not have a thumbnail placed in its tab (or the Location Bar). Setting it to0will prevent thumbnails from being used altogether. The default value is1024pixels.
Note: Firefox 1.5 and above and SeaMonkey only.
browser. chrome. load_toolbar_iconsInteger0(default): Never load site icons/favicons when displaying bookmarks in menus (overridesbrowser.chrome.site_icons)
1: Load site icons/favicons when they've been cached
2: Always load site icons/favicons
browser. chrome. site_iconsBooleanTrue(default): Load and display site icons specified bylinkelement(s) in the web page
False: Opposite of the above
Note: This should be set to the same value asbrowser.chrome.faviconsfor legacy reasons.
browser. chrome. toolbar_styleIntegerSet toolbar style for browser
0: Pictures Only
1: Text Only
2(default): Pictures and Text
browser. chrome. toolbar_tipsBooleanDetermines 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. chromeURLStringLocation of browser's UI chrome; launched at browser startup. Default value ischrome://browser/content/
browser. display. background_colorStringThe default color for the background of browser content as a hex code. This affects blank tabs, web pages whose backgrounds are not explicitly set, and XUL error pages. Default value is#FFFFFF.
Note: In Firefox, this can be changed via " Tools → Options→ Content / Fonts & Colors → Colors... → Text and Background → Background " (Firefox 1.5 and above).
browser. display. focus_background_colorStringThe default color for the background of focused elements as a hex code. Default value is#117722. Requires thatbrowser.display.use_focus_colorsbe true
browser. display. focus_ring_on_anythingBooleanTrue: Display the focus ring (normally only shown on links) on anything
False(default): Display the focus ring on links only
browser. display. focus_ring_widthIntegerDetermines 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 ofnpixels around focused elements
browser. display. focus_text_colorStringThe default color for the text of focused elements as a hex code. Default value is#ffffff. Requires thatbrowser.display.use_focus_colorsbe true
browser. display. force_inline_alttextBooleanTrue: Force broken images'alttext to be displayed inline
False(default): Show an icon if rendering in Quirks Mode and there is noalttext, or if rendering in Quirks Mode and the image has a size specified.
browser. display. foreground_colorStringThe default color for the foreground of browser content as a hex code. This affects web pages whose text colors are not explicity set and XUL error pages. Default value is#000000.
Note: In Firefox, this can be changed via " Tools → Options→ Content / Fonts & Colors → Colors... → Text and Background → Text" (Firefox 1.5 and above).
browser. display. normal_lineheight_calc_controlIntegerDetermine 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_resolutionIntegerFirefox 1.5 onlyDPI of display device. Affects CSSabsolute length units (e.g. pt, mm).
-1(default): Use the operating system's logical resolution or 96 DPI, whichever is greater
0: Force use of operating system's logical resolution
(n): Assume screen DPI ofn. Default DPI is96.
Note: In Firefox, this can be changed via " Tools → Options→ Content → Advanced → Display Resolution". See browser. screen_resolutionfor Firefox 1.0.x or layout. css. dpifor Firefox 2.0+.
browser. display. show_image_placeholdersBooleanTrue(default): Show placeholders while image is loading
False: Opposite of above
browser. display. use_document_colorsBooleanTrue(default): Allow documents to specify colors to use
False: Opposite of above
Note: In Firefox, this can be changed via " Tools → Options→ Content / Fonts & Colors → Colors → Allow pages to chose their own colors, instead of my selections above" (Firefox 1.5 and above).
browser. display. use_document_fontsInteger0: 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 (between0and1) via " Tools → Options→ Content / Fonts & Colors → Advanced → Allow pages to chose their own fonts, instead of my selections above" (Firefox 1.5 and above).
In SeaMonkey, the corresponding setting is Edit → Preferences→ Appearance → Fonts → [√] Allow documents to use other fonts
browser. display. use_focus_colorsBooleanTrue: Set colors on focused items according to preferences
False(default): Do not set colors on focused items
browser. display. use_system_colorsBooleanTrue: Use colors specified by OS to display documents
False(default): Opposite of above
Note: In Firefox, this can be changed via " Tools → Options→ Content / Fonts & Colors → Colors → Use system colors" (Firefox 1.5 and above).
browser. dom. document. all. disabledBooleanTrue: Disables emulation of IE'sdocument.allcollection
False(default): Enable undetectabledocument.allsupport in quirks mode (see bug 248549)
browser. dom. global_scope_pollution. disabledBooleanTrue: Disable the more aggressive emulation of IE's "IDs directly accessible in the global scope" behavior.
False(default): Automatically add IDs to the global (window) scope in quirks mode.
browser. dom. window. dump. enabledBooleanTrue: Enable JavaScript dump() output
False: Opposite of the above
browser. download. defaultFolderStringHolds the path of the default download directory determined frombrowser.download.folderList. Not set by default; set after the user configures their download options.
browser. download. dirStringThe last directory used for saving a file from the "What should (browser) do with this file?" dialog.
browser. download. downloadDirStringDetermines the directory to download to whenbrowser.download.useDownloadDirisfalse. Appears to mirrorbrowser.download.dir.
browser. download. folderListIntegerWhich of several internally-specified locations to use for the default download directory
0: the desktop
1(default): the downloads folder
2: the last folder specified for a download
Note: In Firefox, this can be changed via " Tools → Options→ Main / Downloads → Save files to... (Firefox 2 and above) or Downloads/Download Folder → Save all files to this folder" (Firefox 1.5).
browser. download. hide_plugins_without_extensionsBooleanTrue(default): In the Download Actions dialog, remove entries where no file extensions are associated with a plugin.
False: Opposite of the above.
browser. download. lastDirStringPath to the last directory used for a download via "Save As."
browser. download. manager. alertOnEXEOpenBooleanTrue(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. closeWhenDoneBooleanTrue: Close the Download Manager when all downloads are complete
False(default): Opposite of the above
Note: In Firefox, this can be changed via " Tools → Options→ Main / Downloads → Close it when all downloads are finished" (Firefox 2 and above) or Downloads / Download Manager → Close the Download Manager when all downloads are complete" (Firefox 1.5).
browser. download. manager. flashCountIntegerNumber 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 is2.
browser. download. manager. focusWhenStartingBooleanTrue: 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. openDelayIntegerIf a download takes less than this number of milliseconds to complete, do not open the Download Manager window. Default value is0(always show Download Manager window).
browser. download. manager. retentionIntegerWhen to remove downloaded files' entries from the Download Manager
0: Upon successful download
1: When the browser exits
2(default): Manually
Note: In Firefox, this can be changed via " Tools → Options→ Privacy / History → Remember what I've downloaded" (Firefox 2 and above) or "Privacy → Download History → Remove files from the Download Manager" (Firefox 1.5).
browser. download. manager. showAlertIntervalIntegerNumber of milliseconds after downloads complete to show the "completed" alert. Default value is2000.
browser. download. manager. showAlertOnCompleteBooleanTrue(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. scanWhenDoneBooleanTrue(default): Scan files for viruses when they finish downloading
False: Do not scan downloads for viruses
browser. download. manager. showWhenStartingBooleanTrue(default): Show Download Manager window when a download begins
False: Opposite of the above
Note: In Firefox, this can be changed via " Tools → Options→ Main / Downloads → Show the Downloads window when downloading a file" (Firefox 2 and above) or " Tools → Options→ Downloads / Download Manager → Show Download Manager when a download begins" (Firefox 1.5)
browser. download. manager. skipWinSecurityPolicyChecksBooleanTrue: Bypass the Windows security check (ignore system security settings for executable file downloads).
False:(default) Use Windows' security setting for executable file downloads ("Launching applications and unsafe files" setting in Internet Options). This blocks executable file downloadsif the Windows setting is set to "Disable".
Note: Added in bug 445158for Firefox 3 (3.0.6, 3.1b2 and above). No longer used in Firefox 3.6 and above (removed in bug 504804).
browser. download. manager. useWindowBooleanTrue: Use the Download Manager window for downloads
False: Opposite of the above
Note: In Firefox, this is effectively the same as settingbrowser.download.manager.showWhenStartingto false; the Download Manager is used for downloads regardless of the setting.
Note: This was removed in bug 439495for Firefox 3.1.
browser. download. save_converter_indexIntegerThe format to save web pages in
0: Web Page (Complete)
1: Web Page (HTML Only)
2: Text
Note: In Firefox, this setting is remembered from the option you choose in the Save As dialog.

browser. download. show_plugins_in_listBooleanTrue(default): In the Download Actions dialog, display actions and filetypes associated with installed plugins.
False: Opposite of the above.
browser. download. useDownloadDirBooleanTrue(default): Without asking a location, download files to the directory specified inbrowser.download.folderList
False: Ask where to save every file
Note: In Firefox, this can be changed via " Tools → Options→ Main / Downloads → Always ask me where to save files (Firefox 2 and above) or Downloads / Download Folder → Ask me where to save every file" (Firefox 1.5)
browser. enable_automatic_image_resizingBooleanTrue(default): When viewing an image not in a web page, the image will be resized to fit in the browser window if it is too large for the browser window. The image can be shown in its real size by left clicking on it.
False: Images are always shown in their real size.
Note: In Firefox, this can be changed via " Tools → Options→ Advanced → General → Resize large images to fit in the browser window (Firefox 1.0.x and 1.5)". UI removed in Firefox 2.0+.
browser. feedview. articleLengthInteger Pref removed.Previously:
The number of words per feed item to display. Default value is50.
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. reloadIntervalInteger Pref removed.Previously:
Determines how often in seconds to reload the currently rendered feed. Default value is0(never reload).
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. showBarBoolean Pref removed.Previously:
True(default): Display the options settings in feed view.
False: Opposite of the above
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. showImageBoolean Pref removed.Previously:
True(default): Display images embedded in feed items in-line.
False: Opposite of the above.
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. showMenuBoolean Pref removed.Previously:
True(default): Display a menu alongside rendered feeds with relevant functions
False: Opposite of the above.
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. timerIntervalInteger Pref removed.Previously:
Determines how often to refresh the feed. Default value is0(no refresh).
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. feedview. externalCSSString Pref removed.Previously:
Path to a custom CSS file to apply to feeds. Default value is an empty string.
Note: Feedview functionality was present for only a short while prior to Firefox 1.5 Beta.
browser. fixup. alternate. enabledBooleanTrue(default): Try to fix up http://footo http://(prefix)foo(suffix)
False: Do not second-guess the user
browser. fixup. alternate. prefixStringThe prefix to prepend when attempting to fix an entered URL. Default is "www." (includes full stop). Requiresbrowser.fixup.alternate.enabledbe true.
browser. fixup. alternate. suffixStringThe suffix to append when attempting to fix an entered URL. Default is ".com". Requiresbrowser.fixup.alternate.enabledbe true.
browser. fixup. hide_user_passBooleanTrue(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@foointo http://user:password@(prefix)foo(suffix)but instead http://user@(prefix)foo(suffix))
False: Include entered password in fixed URL
browser. fixup. use-utf8BooleanFirefox 11 / SeaMonkey 2.8 and above only. See bug 647403.
Default:false(buttrueon zh-TW localized builds).
browser. formfill. enableBooleanTrue(default): Save information entered in web page forms and the Search Bar
False: Opposite of the above
Note: In Firefox, this can be changed via " Tools → Options→ Privacy / History → Remember what I enter in forms and the search bar" (Firefox 2 and above) or " Tools → Options→ Privacy → Saved Forms → Save information I enter in forms and the Search Bar" (Firefox 1.5)
browser. forms. submit. backwards_compatibleBooleanTrue(default): Leave off mandatoryContent-Transfer-Encodingheader when submitting HTML forms
False: Send header as the spec requires
Note: Sending the header "used to cause Bad Things, including server crashes" according to comments in the Mozilla source (see bug 83065). Eventually this pref may disappear.
browser. frames. enabledBooleanTrue(default): Enables the display of HTML frames
False: Opposite of the above; displayscontent instead
browser. fullscreen. animateUpIntegerControls toolbar and tab strip animation while in Full Screen.
0: No toolbar and tab strip animation
1(default): Animates only first collapse.
2: Animates each collapse.
browser. fullscreen. autohideBooleanHides toolbar and tab strip when entering Full Screen.
True(default): Shows toolbar and tab strip.
False: Hides toolbar and tab strip
browser. goBrowsing. enabledBooleanTrue(default): If a normal DNS lookup times out, try hitting Google
False: Opposite of the above
Note: No longer used
browser. helperApps. alwaysAsk. forceBooleanTrue: 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. deleteTempFileOnExitBooleanTrue: Delete temporary files on exit. See comment 19 on bug 238789(especially Mac)
False(same as default unset): Opposite of above (keep the files)
browser. helperApps. neverAsk. openFileStringA comma-separated list of MIME types to open directly without asking for confirmation. Default value is an empty string.
browser. helperApps. neverAsk. saveToDiskStringA 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. hiddenWindowChromeURLStringThe chrome:// URL for the hidden window. Used in Mac OS X for when the browser is running but has no windows open. Default value ischrome://browser/content/hiddenWindow.xul
browser. history. groupingStringHow to group entries in the history window (not applicable for Firefox's History sidebar). Default value isday.
browser. history_expire_daysIntegerNumber of maximum days to remember visited pages in history. Default value is9for SeaMonkey and Firefox 2,180for Firefox 3.
Note: In Firefox 2, this can be changed via " Tools → Options→ Privacy → History → Remember visited pages for the last ___ days". No UI for Firefox 3.
browser. history_expire_days_minIntegerNumber of minimum days to remember visited pages in history. Default value is90.
Note: In Firefox 3, this can be changed via “Keep my history for at least ___ days” under “ Tools → Options→ Privacy → History”
browser. history_expire_sitesIntegerMaximum number of websites to keep in history. Default value is40000.
browser. jsannoyances. disabledBooleanThe collective state of several other preferences; namely,dom.event.contextmenu.enabled,dom.disable_window_move_resize,dom.disable_window_flip,dom.disable_window_open_feature.status, anddom.disable_window_status_change. Used by the preferences dialog for tracking; changing the value of this preference manually does not change the tracked preferences.
True: Consider all of the above preferences to be true (exceptdom.event.contextmenu.enabled, which is considered to be false)
False(default): Opposite of the above
Note: Firefox 1.5 and above only.
browser. link. open_externalIntegerWhere to open links sent to the browser from an external application
2(default in SeaMonkey): Opens external links in a new window
3(default in Firefox): Opens external links in a new tab in the most recent window
1(or anything else): Opens external links in current window
Note: In Firefox 1.5, this can be changed via " Tools → Options→ Tabs → Open links from other applications in:"; in Firefox 2 and above, via “Tools → Options → Tabs → New pages should be opened in:” (same asbrowser.link. open_newwindow) and in SeaMonkey, via " Edit -> Preferences-> Navigator -> Tabbed browsing / Links from other applications -> Open links passed from another applications in".
Pref removed from Firefox 3.5
browser. link. open_newwindowIntegerWhere to open links that would normally open in a new window
2(default in SeaMonkey and Firefox 1.5): In a new window
3(default in Firefox 2 and above): In a new tab
1(or anything else): In the current tab or window
Note: In Firefox 1.5, this can be changed via " Tools → Options→ Tabs → Force links that open new windows to open in:"; in Firefox 2 and above, via “Tools → Options → Tabs → New pages should be opened in:” (same as browser.link.open_external) and, in SeaMonkey, via " Edit -> Preferences-> Navigator -> Tabbed browsing / Link open behavior -> Open links meant to open a new window in".
browser. link. open_newwindow. restrictionIntegerFirefox and SeaMonkey only. Source: The Burning Edge.
0(Default in Firefox 1.0.x and SeaMonkey): Force all new windows opened by JavaScript into tabs.
1: Let all windows opened by JavaScript open in new windows. (Default behavior in IE.)
2(Default in Firefox 1.5 and above): Catch new windows opened by JavaScript that do not have specific values set (how large the window should be, whether it should have a status bar, etc.) This is useful because some popups are legitimate — it really is useful to be able to see both the popup and the original window at the same time. However, most advertising popups also open in new windows with values set, so beware.
browser. link. open_newwindow. uiIntegerDetermine which new window open options are available from the UI. No longer used in Firefox 1.0. Default value is3.
browser. microsummary. enabledBooleanTrue(default): Allow the microsummary serviceto retrieve information for bookmarks with microsummaries.
False: Prevent microsummary updates to bookmarks.
browser. microsummary. generatorUpdateIntervalIntegerDetermines how often to check for updates to microsummary generators when generator updates are enabled. A non-negative integer, in seconds, determine

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