About:config: Difference between revisions

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{{wrongtitle|title=about:config}}
{{wrongtitle|title=about:config}}
''about:config'' is a feature of Mozilla applications which lists application settings (known as ''preferences'') that are read from the profile files [[prefs.js file|prefs.js]] and [[user.js]], and from application defaults. Many of these preferences are not present in the  Options or Preferences dialog. Using about:config is one of [[Editing configuration | several methods]] of modifying preferences and adding other "hidden" ones.
''about:config'' is a feature of Mozilla applications which lists application settings (known as ''preferences'') that are read from the profile files [[prefs.js file|prefs.js]] and [[user.js]], and from application defaults. Many of these preferences are not present in the  Options or Preferences dialog. Using about:config is one of [[Editing configuration | several methods]] of modifying preferences and adding other "hidden" ones.
This article is a '''companion article''' for '''[[about:config entries]]''' where the most important '''about:config''' variables are described.


'''Warning''': 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.  
'''Warning''': 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.  


==Opening about:config==
==Opening about:config==
* In '''Firefox and Mozilla Suite/SeaMonkey''', type '''about:config''' in the Location Bar (address bar) and press Enter to display the list of preferences, as shown below in Firefox 3. If you see a page with the warning message, ''This might void your warranty!'', click the button labeled  "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).  ''Use the checkbox there to avoid the warning in the future.''
* In '''Firefox and Mozilla Suite/SeaMonkey''', type '''about:config''' in the Location Bar (address bar) and press Enter to display the list of preferences, as shown below in Firefox 14 on Windows 7. If you see a page with the warning message, ''This might void your warranty!'', click the button labeled  "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).  ''Use the checkbox there to avoid the warning in the future.''
:[[Image:Fx3aboutconfig.png]]
:[[Image:Aboutconfig-fx40win.png]]
* In '''Thunderbird''' 1.5 or later, about:config is accessed via "[[Menu differences in Windows, Linux, and Mac|Tools -> Options]] -> Advanced -> General -> Config Editor (button)". To access this and other about:* functions more easily in Thunderbird, you can use [https://addons.mozilla.org/thunderbird/addon/9695 ViewAbout add-on].
* In '''Thunderbird''' 1.5 or later, about:config is accessed via "[[Menu differences in Windows, Linux, and Mac|Tools -> Options]] -> Advanced -> General -> Config Editor (button)". To access this and other about:* functions more easily in Thunderbird, you can use [https://addons.mozilla.org/thunderbird/addon/9695 ViewAbout add-on].
* For [http://www.nvu.com Nvu], there's a compatible version of the AboutConfig extension [http://glazman.org/nvu/releases/extensions/ here].
* For [http://www.nvu.com Nvu], there's a compatible version of the AboutConfig extension [http://glazman.org/nvu/releases/extensions/ here].


==Adding modifying and resetting preferences==  
==Adding modifying and resetting preferences==  
[[Image:Fx3aboutconfig-ContextMenu.png|right]]  
[[Image:AboutconfigContextMenu-fx40.png|right]]  
To add a new preference, context-click (right-click) anywhere in the list of preferences.  In the context menu, select ''New'' then select the type of preference you are adding.
To add a new preference, context-click (right-click) anywhere in the list of preferences.  In the context menu, select ''New'' then select the type of preference you are adding.
*'''String''' is any sequence of text  
*'''String''' is any sequence of text  
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*'''Boolean''' is true-false
*'''Boolean''' is true-false


To modify an existing preference, context-click (right-click) on the preference, select ''Modify'' and type in the new value.  In some cases, ''Toggle'' will be the selection offered for boolean (true-false) preferences.
To modify an existing preference, context-click (right-click) on the preference.  For string or integer preferences, select ''Modify'' in the context menu and type in the new value.  For boolean (true-false) preferences, ''Toggle'' will be the selection offered.


To reset a preference to its default value or to remove an added preference,  context-click (right-click) on the preference and select ''Reset''. 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 [[Resetting preferences|this article]]).
To reset a preference to its default value or to remove an added preference,  context-click (right-click) on the preference and select ''Reset''. 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 [[Resetting preferences|this article]]).


==Filter bar==
==Search bar==
You can use the ''Filter'' bar at the top of the ''about:config'' page to filter the preferences that you want to inspect.  ''The filter bar is case-insensitive unlike the actual configuration variables.''  
You can use the "Search" bar at the top of the ''about:config'' page ("Filter" bar in older versions) to filter the preferences that you want to inspect.  ''The search bar is case-insensitive, unlike the actual configuration variables.''  


Some examples to filter results:
Some examples to filter results:
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'''Regular Expressions:''' Starting with Firefox 3, the Filter bar also accepts wildcards and a [http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Guide/Regular_Expressions regular expression] in the form of <code>/regexp/i</code> to filter preferences.  [https://bugzilla.mozilla.org/show_bug.cgi?id=213832] The ''i'' switch is for ignore case. That is the default for normal searches, but you need to specify it if you want the [https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Global_Objects/RegExp RegExp] match to be case insensitive.  The RegExp tests for a match of ''name;value'' of a preference.  
'''Regular Expressions:''' Starting with Firefox 3, the Filter bar also accepts wildcards and a [https://developer.mozilla.org/en-US/docs/JavaScript/Guide/Regular_Expressions regular expression] in the form of <code>/regexp/i</code> to filter preferences.  [https://bugzilla.mozilla.org/show_bug.cgi?id=213832] The ''i'' switch is for ignore case. That is the default for normal searches, but you need to specify it if you want the [https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/RegExp RegExp] match to be case insensitive.  The RegExp tests for a match of ''name;value'' of a preference.  


Some examples of '''regular expressions''' (RegExp) to filter results
Some examples of '''regular expressions''' (RegExp) to filter results
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==External links==
==External links==
* [https://developer.mozilla.org/En/A_Brief_Guide_to_Mozilla_Preferences A Brief Guide to Mozilla Preferences - MDC]
* [https://developer.mozilla.org/docs/Mozilla/Preferences/A_brief_guide_to_Mozilla_preferences A Brief Guide to Mozilla Preferences - MDN]
* [http://web.archive.org/web/20080620000813/http://www.mozillazine.org/misc/about:config/ How To Modify Hidden Preferences Using about:config] &mdash; MozillaZine's step by step guide with screenshots  (from web.archive.org)
* [http://web.archive.org/web/20080620000813/http://www.mozillazine.org/misc/about:config/ How To Modify Hidden Preferences Using about:config] &mdash; MozillaZine's step by step guide with screenshots  (from web.archive.org)
* [http://ilias.ca/archive/mozilla/customizing/ Mozilla Help: Editing Configuration files] &mdash;  (from ilias.ca)  
* [http://seamonkey.ilias.ca/customizing/ SeaMonkey Help: Editing config files] &mdash;  (from ilias.ca)
* [http://preferential.mozdev.org/ Preferential extension] &mdash; An extension similar to about:config with extra features, such as documentation for some preferences.
* [https://support.mozilla.org/kb/about-config-editor-firefox Configuration Editor for Firefox] (Mozilla Support)
* [https://support.mozilla.org/kb/config-editor Config Editor] for Thunderbird  (Mozilla Support)


[[Category:Configuration]]
[[Category:Configuration]]
[[Category:Configuration (Thunderbird)]]
[[Category:Configuration (Thunderbird)]]

Revision as of 11:52, 5 September 2015

about:config is a feature of Mozilla applications which lists application settings (known as preferences) that are read from the profile files prefs.js and user.js, and from application defaults. Many of these preferences are not present in the Options or Preferences dialog. Using about:config is one of several methods of modifying preferences and adding other "hidden" ones.

This article is a companion article for about:config entries where the most important about:config variables are described.

Warning: 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.

Opening about:config

  • In Firefox and Mozilla Suite/SeaMonkey, type about:config in the Location Bar (address bar) and press Enter to display the list of preferences, as shown below in Firefox 14 on Windows 7. If you see a page with the warning message, This might void your warranty!, click the button labeled "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). Use the checkbox there to avoid the warning in the future.
  • In Thunderbird 1.5 or later, about:config is accessed via "Tools -> Options -> Advanced -> General -> Config Editor (button)". To access this and other about:* functions more easily in Thunderbird, you can use ViewAbout add-on.
  • For Nvu, there's a compatible version of the AboutConfig extension here.

Adding modifying and resetting preferences

To add a new preference, context-click (right-click) anywhere in the list of preferences. In the context menu, select New then select the type of preference you are adding.

  • String is any sequence of text
  • Integer is a number
  • Boolean is true-false

To modify an existing preference, context-click (right-click) on the preference. For string or integer preferences, select Modify in the context menu and type in the new value. For boolean (true-false) preferences, Toggle will be the selection offered.

To reset a preference to its default value or to remove an added preference, context-click (right-click) on the preference and select Reset. 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 this article).

Search bar

You can use the "Search" bar at the top of the about:config page ("Filter" bar in older versions) to filter the preferences that you want to inspect. The search bar is case-insensitive, unlike the actual configuration variables.

Some examples to filter results:
  browser.tabs.
  newtab


Regular Expressions: Starting with Firefox 3, the Filter bar also accepts wildcards and a regular expression in the form of /regexp/i to filter preferences. [1] The i switch is for ignore case. That is the default for normal searches, but you need to specify it if you want the RegExp match to be case insensitive. The RegExp tests for a match of name;value of a preference.

Some examples of regular expressions (RegExp) to filter results
  security*ssl
  security*ssl*rsa
  security*tls
  /^security[.]ssl3.*rsa|security[.].*tls/i
  /^security[.]ssl3.*(128|256)/i
  /^(?!gecko[.]handler|network[.]IDN|network[.]protocol|print|security[.]ssl)/i
  /^(?=browser[.]|dom[.]|network[.](?!IDN|protocol))/i

See also

External links