Join MDN and developers like you at Mozilla's View Source conference, 12-14 September in Berlin, Germany. Learn more at https://viewsourceconf.org

Preference reference

Draft
This page is not complete.

accessibility.tabfocus
The preference accessibility.tabfocus controls what elements receive focus when the user presses the Tab key.
browser.altClickSave
The preference browser.altClickSave controls whether clicking a link while holding the alt key starts the download of that link.
browser.dom.window.dump.enabled
This setting enables the dump function, which sends messages to the system console. Set it to true to enable it, or false to disable it.
browser.dom.window.dump.file
browser.dom.window.dump.file redirects the ouput of window.dump() calls to a file whose address is specified in this preference if browser.dom.window.dump.enabled is set to true. Changes require an application restart.
browser.download.lastDir.savePerSite
browser.download.lastDir.savePerSite controls whether the directory preselected in the file picker for saving a file download is being remembered on a per-website (host) base. If set to true, the data is stored as content preference.
browser.pagethumbnails.capturing_disabled
The preference browser.pagethumbnails.capturing_disabled controls whether the application creates screenshots of visited pages which will be shown if the web page is shown in the grid of the "New Tab Page" (about:newtab) which offers the most often visited pages for fast navigation.
browser.search.context.loadInBackground
browser.search.context.loadInBackground controls whether a search from the context menu with "Search <search engine> for <selected text>" opening a new tab will give focus to it and load it in the foreground or keep focus on the current tab and open it in the background.
browser.urlbar.formatting.enabled
The preference browser.urlbar.formatting.enabled controls whether the domain name including the top level domain is highlighted in the address bar by coloring it black and the other parts grey.
browser.urlbar.trimURLs
The preference browser.urlbar.trimURLs controls whether the protocol http and the trailing slash behind domain name (if the open page is exactly the domain name) are hidden.
dom.event.clipboardevents.enabled
dom.event.clipboardevents.enabled lets websites get notifications if the user copies, pastes, or cuts something from a web page, and it lets them know which part of the page had been selected. The emitting of the oncopy, oncut and onpaste events are controlled by this preference.
javascript.options.showInConsole
The preference javascript.options.showInConsole controls whether errors or warnings in chrome code are shown in the Error Console.
javascript.options.strict
JavaScript warnings are generated when code is executed that doesn't cause a run-time error, but is non-standard, poorly written, or prone to cause logic errors. This preference controls whether JavaScript warnings are logged to the JavaScript Console.
mail.tabs.drawInTitlebar
Starting in Thunderbird 17.0, the tabs are drawn in the title bar. The old behavior can be restored by setting the preference mail.tabs.drawInTitlebar to false.
nglayout.debug.disable xul fastload
The preference nglayout.debug.disable_xul_fastload controls whether or not XUL fastload is used.
nglayout.debug.disable_xul_cache
To improve performance, Mozilla caches chrome XUL documents the first time they load for faster loading later. The effect is that the source XML file is not read and re-parsed each time the chrome in question is displayed. The XUL cache is serialized and saved between Mozilla sessions in the XUL FastLoad file, which saves a “compiled” version of the XUL and JavaScript in a document to disk for faster startup the next time the application runs.
reader.parse-on-load.force-enabled
The preference reader.parse-on-load.force-enabled controls if the reader mode used in Firefox Mobile should be enabled independent of the memory available in the device. By default, the reader mode in Firefox Mobile is only enabled if the memory is greater than 384MB.
ui.SpellCheckerUnderline
ui.SpellCheckerUnderline holds the colour which is used to underline words not recognized by the spellchecker.
ui.SpellCheckerUnderlineStyle
ui.SpellCheckerUnderlineStyle holds the style which is used to underline words not recognized by the spellchecker.
ui.alertNotificationOrigin
ui.alertNotificationOrigin controls the position and direction from which popup notifications invoked by nsIAlertsService are sliding in.
ui.textSelectBackground
ui.textSelectBackground saves the color in which the background of a text selection in the user interface or in content will be styled.
ui.textSelectForeground
ui.textSelectForeground saves the color in which the text of a text selection in the user interface or the content will be styled.
ui.tooltipDelay
ui.tooltipDelay stores the delay in milliseconds between the mouse stopping over an element and the appearing of its tooltip.
view_source.syntax_highlight
The preference view_source.syntax_highlight controls whether markup in the view source view is syntax highlighted.

Document Tags and Contributors

 Contributors to this page: Sheppy, jswisher, ziyunfei
 Last updated by: Sheppy,