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<!DOCTYPE html> <html class="client-nojs" lang="en" dir="ltr"> <head> <meta charset="UTF-8"/> <title>About:config - MozillaZine Knowledge Base</title> <script>document.documentElement.className="client-js";RLCONF={"wgBreakFrames":false,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"019ee7f0b50cb0a5068b62e5","wgCSPNonce":false,"wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"About:config","wgTitle":"About:config","wgCurRevisionId":47114,"wgRevisionId":47114,"wgArticleId":1739,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["Configuration","Configuration (Thunderbird)"],"wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"About:config","wgRelevantArticleId":1739,"wgIsProbablyEditable":false,"wgRelevantPageIsProbablyEditable":false,"wgRestrictionEdit":[],"wgRestrictionMove":[]};RLSTATE={"site.styles":"ready", "user.styles":"ready","user":"ready","user.options":"loading","skins.monobook.styles":"ready"};RLPAGEMODULES=["site","mediawiki.page.ready","mediawiki.toc","skins.monobook.scripts"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.implement("user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"});});});</script> <link rel="stylesheet" href="/load.php?lang=en&modules=skins.monobook.styles&only=styles&skin=monobook"/> <script async="" src="/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=monobook"></script> <meta name="generator" content="MediaWiki 1.40.1"/> <meta name="robots" content="max-image-preview:standard"/> <meta name="format-detection" content="telephone=no"/> <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes, minimum-scale=0.25, maximum-scale=5.0"/> <link rel="icon" href="/favicon.ico"/> <link rel="search" type="application/opensearchdescription+xml" href="/opensearch_desc.php" title="MozillaZine Knowledge Base (en)"/> <link rel="EditURI" type="application/rsd+xml" href="//kb.mozillazine.org/api.php?action=rsd"/> <link rel="alternate" type="application/atom+xml" title="MozillaZine Knowledge Base Atom feed" href="/index.php?title=Special:RecentChanges&feed=atom"/> </head> <body class="mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject page-About_config rootpage-About_config skin-monobook action-view skin--responsive"><div id="globalWrapper"> <div id="column-content"> <div id="content" class="mw-body" role="main"> <a id="top"></a> <div id="siteNotice"></div> <div class="mw-indicators"> </div> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">About:config</span></h1> <div id="bodyContent" class="monobook-body"> <div id="siteSub">From MozillaZine Knowledge Base</div> <div id="contentSub" ><div id="mw-content-subtitle"></div></div> <div id="jump-to-nav"></div><a href="#column-one" class="mw-jump-link">Jump to navigation</a><a href="#searchInput" class="mw-jump-link">Jump to search</a>  <div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="en" dir="ltr"><div class="mw-parser-output"><div class="boilerplate metadata" id="wrongtitle" style="background: #f7fbff; margin: .5em 2.5%; padding: 0 1em; border: 1px solid #79b"> <p>The correct title of this article is <b>about:config</b>. It appears incorrectly here due to <a href="http://www.wikipedia.org/wiki/Wikipedia:Naming_conventions_(technical_restrictions)" class="extiw" title="wikipedia:Wikipedia:Naming conventions (technical restrictions)">technical limitations</a> in the wiki software. </p> </div> <p><i>about:config</i> is a feature of Mozilla applications which lists application settings (known as <i>preferences</i>) that are read from the profile files <a href="/Prefs.js_file" title="Prefs.js file">prefs.js</a> and <a href="/User.js" class="mw-redirect" title="User.js">user.js</a>, and from application defaults. Many of these preferences are not present in the Options or Preferences dialog. Using about:config is one of <a href="/Editing_configuration" title="Editing configuration"> several methods</a> of modifying preferences and adding other "hidden" ones. </p><p>This article is a <b>companion article</b> for <b><a href="/About:config_entries" title="About:config entries">about:config entries</a></b> where the most important <b>about:config</b> variables are described. </p><p><b>Warning</b>: Modifying preferences can, in rare circumstances, break Firefox, Thunderbird or the Mozilla Suite, or can cause strange behavior. Only do so if you know what you are doing or are following trustworthy advice. </p> <div id="toc" class="toc" role="navigation" aria-labelledby="mw-toc-heading"><input type="checkbox" role="button" id="toctogglecheckbox" class="toctogglecheckbox" style="display:none" /><div class="toctitle" lang="en" dir="ltr"><h2 id="mw-toc-heading">Contents</h2><span class="toctogglespan"><label class="toctogglelabel" for="toctogglecheckbox"></label></span></div> <ul> <li class="toclevel-1 tocsection-1"><a href="#Opening_about:config"><span class="tocnumber">1</span> <span class="toctext">Opening about:config</span></a></li> <li class="toclevel-1 tocsection-2"><a href="#Adding_modifying_and_resetting_preferences"><span class="tocnumber">2</span> <span class="toctext">Adding modifying and resetting preferences</span></a></li> <li class="toclevel-1 tocsection-3"><a href="#Search_bar"><span class="tocnumber">3</span> <span class="toctext">Search bar</span></a></li> <li class="toclevel-1 tocsection-4"><a href="#See_also"><span class="tocnumber">4</span> <span class="toctext">See also</span></a></li> <li class="toclevel-1 tocsection-5"><a href="#External_links"><span class="tocnumber">5</span> <span class="toctext">External links</span></a></li> </ul> </div> <h2><span class="mw-headline" id="Opening_about:config">Opening about:config</span></h2> <ul><li>In <b>Firefox and SeaMonkey</b>, type <b>about:config</b> in the Location Bar (address bar) and press Enter to display the list of preferences, as shown below in Firefox on Windows 7. If you see a page with the warning message, <i>This might void your warranty!</i>, click the button labeled "I accept the risk" or "I'll be careful, I promise!" to continue. (In fact, there is no warranty whatsoever, it's more a joke to ensure that users are aware of what they are about to do.) <i>Use the checkbox there to avoid the warning in the future.</i></li></ul> <dl><dd><span class="mw-default-size" typeof="mw:File"><a href="/File:Aboutconfig-fx40win.png" class="mw-file-description"><img src="/images/Aboutconfig-fx40win.png" decoding="async" width="550" height="339" /></a></span></dd></dl> <ul><li>In <b>Thunderbird</b>, about:config is accessed via "<a href="/Menu_differences_in_Windows,_Linux,_and_Mac" title="Menu differences in Windows, Linux, and Mac">Tools -> Options</a> -> Advanced -> General -> Config Editor (button)". To access this and other about:* functions more easily in Thunderbird, you can use <a rel="nofollow" class="external text" href="https://addons.mozilla.org/thunderbird/addon/9695">ViewAbout add-on</a>.</li></ul> <h2><span class="mw-headline" id="Adding_modifying_and_resetting_preferences">Adding modifying and resetting preferences</span></h2> <figure class="mw-default-size mw-halign-right" typeof="mw:File"><a href="/File:AboutconfigContextMenu-fx40.png" class="mw-file-description"><img src="/images/AboutconfigContextMenu-fx40.png" decoding="async" width="226" height="167" /></a><figcaption></figcaption></figure> <p>To add a new preference, context-click (right-click) anywhere in the list of preferences. In the context menu, select <i>New</i> then select the type of preference you are adding. </p> <ul><li><b>String</b> is any sequence of text</li> <li><b>Integer</b> is a number</li> <li><b>Boolean</b> is true-false</li></ul> <p>To modify an existing preference, context-click (right-click) on the preference. For string or integer preferences, select <i>Modify</i> in the context menu and type in the new value. For boolean (true-false) preferences, <i>Toggle</i> will be the selection offered. </p><p>To reset a preference to its default value or to remove an added preference, context-click (right-click) on the preference and select <i>Reset</i>. If you added the entry via about:config, the preference will no longer be listed after restarting the program. (For more information about resetting preferences, see <a href="/Resetting_preferences" title="Resetting preferences">this article</a>). </p> <h2><span class="mw-headline" id="Search_bar">Search bar</span></h2> <p>You can use the "Search" bar at the top of the <i>about:config</i> page ("Filter" bar in older versions) to filter the preferences that you want to inspect. <i>The search bar is case-insensitive, unlike the actual configuration variables.</i> </p><p>Some examples to filter results: <br />  browser.tabs. <br />  newtab </p><p><br /> <b>Regular Expressions:</b> Starting with Firefox 3, the Filter bar also accepts wildcards and a <a rel="nofollow" class="external text" href="https://developer.mozilla.org/en-US/docs/JavaScript/Guide/Regular_Expressions">regular expression</a> in the form of <code>/regexp/i</code> to filter preferences. <a rel="nofollow" class="external autonumber" href="https://bugzilla.mozilla.org/show_bug.cgi?id=213832">[1]</a> The <i>i</i> switch is for ignore case. That is the default for normal searches, but you need to specify it if you want the <a rel="nofollow" class="external text" href="https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/RegExp">RegExp</a> match to be case insensitive. The RegExp tests for a match of <i>name;value</i> of a preference. </p><p>Some examples of <b>regular expressions</b> (RegExp) to filter results <br />  security*ssl <br />  security*ssl*rsa <br />  security*tls <br />  /^security[.]ssl3.*rsa|security[.].*tls/i <br />  /^security[.]ssl3.*(128|256)/i <br />  /^(?!gecko[.]handler|network[.]IDN|network[.]protocol|print|security[.]ssl)/i <br />  /^(?=browser[.]|dom[.]|network[.](?!IDN|protocol))/i </p> <h2><span class="mw-headline" id="See_also">See also</span></h2> <ul><li>The article <a href="/About:config_entries" title="About:config entries">about:config entries</a> contains a list of valid about:config entries and their possible values. The article is a reference for what each preference does; it is not the place to actually edit your preferences! (See the section <a class="mw-selflink-fragment" href="#Opening_about:config"> Opening about:config</a> above.)</li> <li><a href="/Editing_configuration" title="Editing configuration">Editing configuration</a></li> <li><a href="/About_protocol_links" title="About protocol links">About protocol links</a> — other about: pages.</li></ul> <h2><span class="mw-headline" id="External_links">External links</span></h2> <ul><li><a rel="nofollow" class="external text" href="https://developer.mozilla.org/docs/Mozilla/Preferences/A_brief_guide_to_Mozilla_preferences">A Brief Guide to Mozilla Preferences - MDN</a></li> <li><a rel="nofollow" class="external text" href="http://web.archive.org/web/20080620000813/http://www.mozillazine.org/misc/about:config/">How To Modify Hidden Preferences Using about:config</a> — MozillaZine's step by step guide with screenshots (from web.archive.org)</li> <li><a rel="nofollow" class="external text" href="http://seamonkey.ilias.ca/customizing/">SeaMonkey Help: Editing config files</a> — (from ilias.ca)</li> <li><a rel="nofollow" class="external text" href="https://support.mozilla.org/kb/about-config-editor-firefox">Configuration Editor for Firefox</a> (Mozilla Support)</li> <li><a rel="nofollow" class="external text" href="https://support.mozilla.org/kb/config-editor">Config Editor</a> for Thunderbird (Mozilla Support)</li></ul>    </div> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="http://kb.mozillazine.org/index.php?title=About:config&oldid=47114">http://kb.mozillazine.org/index.php?title=About:config&oldid=47114</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/Special:Categories" title="Special:Categories">Categories</a>: <ul><li><a href="/Category:Configuration" title="Category:Configuration">Configuration</a></li><li><a href="/Category:Configuration_(Thunderbird)" title="Category:Configuration (Thunderbird)">Configuration (Thunderbird)</a></li></ul></div></div>  <div class="visualClear"></div> </div> </div> <div class="visualClear"></div> </div> <div id="column-one" > <h2>Navigation menu</h2> <div role="navigation" class="portlet" id="p-cactions" aria-labelledby="p-cactions-label"> <h3 id="p-cactions-label" >Page actions</h3> <div class="pBody"> <ul > <li id="ca-nstab-main" class="selected mw-list-item"><a href="/About:config" title="View the content page [c]" accesskey="c">Page</a></li><li id="ca-talk" class="mw-list-item"><a href="/Talk:About:config" rel="discussion" title="Discussion about the content page [t]" accesskey="t">Discussion</a></li><li id="ca-view" class="selected mw-list-item"><a href="/About:config">Read</a></li><li id="ca-viewsource" class="mw-list-item"><a href="/index.php?title=About:config&action=edit" title="This page is protected.
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