About URI scheme
1260694
225729965
2008-07-15T03:13:31Z
Catcrewser
7171334
Just found about:about under common addresses, undoing what I just added.
{{lowercase|about: URI scheme}}
'''about:''' is an internal [[URI scheme]] (also known as a "[[Uniform Resource Locator|URL]] scheme" or, erroneously, "[[protocol (computing)|protocol]]") in various [[web browser]]s to display certain built-in functions. It is not an officially registered scheme, and has no standard syntax.
In early versions of [[Netscape Navigator|Netscape]], any address beginning <code>about:</code> which wasn't recognised as a built-in command would simply result in the text after the colon being displayed. Similarly, in early versions of [[Internet Explorer]], <code>about:</code> followed by a string of [[HTML]] (e.g. <code><nowiki>about:<em>hello world</em></nowiki></code>) would render that string as though it was the source of the page - thus providing a similar (though more limited) facility to the [[data: URI scheme]] defined by RFC 2397. Still other versions of Netscape would return various phrases in response to an unknown <code>about:</code> address, including "Whatchew talkin' 'bout, Willis?" (a catch phrase from the TV show [[Diff'rent Strokes]]) or "Homey don't play dat!" (from a recurring [[Sketch comedy|skit]] on the TV show ''[[In Living Color]]'').
The most commonly implemented <tt>about:</tt> URIs are <code>about:blank</code>, which displays a blank HTML document, and simply <code>about:</code>, which may display information about the browser. [[Opera (web browser)|Opera]] uses URIs beginning with <tt>opera:</tt> for similar purposes, and many <tt>about:</tt> URIs will be translated into an appropriate <tt>opera:</tt> URI if entered; an exception is <code>about:blank</code>, which is not translated.
<blockquote>'''''Note:''' In more recent versions of Internet Explorer, many of the following do not work:''</blockquote>
==Common about: addresses==
{| class="wikitable"
|+'''Common about: addresses'''
! Addresses
! [[Mozilla Application Suite|Mozilla]]/[[SeaMonkey]]
! [[Mozilla Firefox]]
! [[Opera (web browser)|Opera]]
! [[Internet Explorer]]
! [[Konqueror]]
! [[Safari (web browser)|Safari]]
|-
| '''about:'''
| colspan="2" | Shows version information and copyright information
| Translated to "opera:about"
|
| Translated to "about:konqueror"
|
|-
| '''about:about'''
| Lists all the about: addresses
|
| Translated to "opera:about"
|
| Translated to "about:konqueror"
|
|-
| '''about:blank'''{{ref|aboutblank}}
| colspan="6" | Shows a blank HTML document
|-
| '''about:plugins'''
| colspan="2" | Shows the filename, [[MIME type]], description, suffix, and status of all installed plug-ins
| Translated to "opera:plugins"
|
| Shows the filename, [[MIME type]], description, suffix, and status of all installed plug-ins
|-
| '''about:cache'''
| colspan="2" | Shows information about the Cache Service.
| Translated to "opera:cache"
|
| Translated to "about:konqueror"
|-
| '''about:mozilla'''
| colspan="2" | Shows a page from the fictional ''[[The Book of Mozilla|Book of Mozilla]]''. In some versions of Netscape, also replaced the meteors in the standard Netscape [[throbber]] with a large fire-breathing lizard.
|
| The Windows version of IE showed a blank HTML document with [[blue]] background color. Possibly a joke reference to the "[[Blue Screen of Death]]". Removed in [[Windows XP]] [[Service pack|SP2]] but it can still be shown by typing "''res://mshtml.dll/about.moz''" instead.
| Translated to "about:konqueror"
|-
|}
==Mozilla-specific about: addresses==
<!-- Deleted image removed: [[Image:BookofMozilla.PNG|thumb|The Book of Mozilla can be viewed using '''about:mozilla''']] -->
{| class="wikitable"
|+'''Mozilla-specific about: addresses'''
! Addresses
! [[Mozilla Application Suite]] / [[SeaMonkey]]
! [[Mozilla Firefox]]
|-
| '''about:bloat'''
|
| Displays [http://www.mozilla.org/projects/xpcom/MemoryTools.html#BloatView BloatView] output (disabled in release builds).
|-
| '''about:blocked'''
|
| Shows the [[malware]] protection page used when the browser identify some page as not safe for viewing. (Firefox 3-specific).
|-
| '''about:buildconfig'''
| colspan="2" | Shows the arguments and options used to compile the build in use
|-
| '''about:cache'''
| colspan="2" | Shows information about the Cache Service. Number of entries, location of cache, size of cache, etc. for both memory and disk cache.
|-
| '''about:cache?device=memory'''
| colspan="2" | Shows individual entries in memory
|-
| '''about:cache?device=disk'''
| colspan="2" | Shows individual entries on disk
|-
| '''about:cache?device=offline'''
| colspan="2" | Shows individual entries for offline viewing. New to products based on Gecko 1.9 or later.
|-
| '''about:cache-entry'''
| colspan="2" | Shows information about a cache entry. Used in about:cache links. Requires parameters.
|-
| '''about:config'''
| colspan="2" | Shows an interface for viewing and setting a wide variety of configuration variables, many of which are not otherwise accessible through the [[graphical user interface|GUI]] (options panels)
|-
| '''about:crashes'''
| colspan="2" | Shows details of crashes submitted by Mozilla's crash reporter (since Firefox 3).
|-
| '''about:credits'''
| colspan="2" | Shows a list of all those who contributed to Mozilla
|-
| '''about:logo'''
| colspan="2" | Shows the logo used on the '''about:''' screen
|-
| '''about:licence'''
| colspan="2" | In the British English [[Internationalization and localization|localised]] version, shows the content of '''about:license''' but with all occurrences of ''license'' used as a [[noun]] replaced with ''licence'' (see [[American and British English spelling differences]])
|-
| '''about:license'''
| colspan="2" | Shows the [[Mozilla Public License]] (and the [[Netscape Public License]]) for the piece of software. (Only in products based on Gecko 1.8 or later)
|-
| '''about:mozilla'''
| colspan="2" | easter egg: Shows a verse from [[The Book of Mozilla]]
|-
| '''about:neterror'''
| colspan="2" | Shows the error page used when the browser could not access the requested path.
|-
| '''about:plugins'''
| colspan="2" | Shows installed plug-ins.
|-
| '''about:robots'''
|
| Easter egg, beginning with March 8th, 2008 trunk builds.[https://bugzilla.mozilla.org/show_bug.cgi?id=417302]
|}
==Flock-specific about: addresses==
Beginning in Flock 0.9, Flock introduced a feature called My World, a place where your favourites, RSS feeds and favourite media can be found.
{| class="wikitable"
! Address
! [[Flock (web browser)|Flock]]
|-
| '''about:myworld'''
| Shows the My World page.
|-
|}
==Opera-specific about: addresses==
about: is an alias for opera:, therefore all these addresses also work with about: prefixed. User [[JavaScript]] is disabled for all addresses in the about: or opera: URI schemes as a security feature. These pages can, however, be styled using local [[Cascading Style Sheets|stylesheets]].
None of these functions, except the about:blank combination, work in the [[Nintendo DS]] version of the Opera browser, the [[Nintendo DS Browser]].
{| class="wikitable"
|+'''Opera-specific about: addresses'''
! Addresses
! [[Opera (web browser)|Opera]]
|-
| '''opera:blank'''
| Maps to about:blank
|-
| '''opera:about'''
| Provides info about the browser and the configured paths.
|-
| '''about:opera'''
| Maps to opera:about
|-
| '''opera:cache'''
| Shows the content of the cache.
|-
| '''opera:config'''
| (Opera 9.0 and newer) Shows a page that allows changing of numerous browser preferences, many of which cannot be accessed through the normal Preferences window
|-
| '''opera:drives'''
| Shows the local drives of the host system.
|-
| '''opera:history'''
| Shows the content of the browser history.
|-
| '''opera:plugins'''
| Shows installed plug-ins.
|-
| '''opera:button'''
| Defines a custom button as a set of Opera actions.
|-
| '''opera:help'''
| Shortcut to the help directory. This can be either local or external.
|-
|}
==Internet Explorer-specific about: addresses==
'''Note:''' Internet Explorer about: addresses are configurable in [[Microsoft Windows|Windows]]. It is therefore possible that some of the listed addresses don't work. For example "[[The Book of Mozilla|about:mozilla]]" was removed in SP2 (although the page can still be found at "res://mshtml.dll/about.moz"). <!-- To configure about: addresses, open the Registry Editor and browse to: "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\AboutURLs". --> These about: addresses are sometimes used for spyware and adware, most notably in [[CoolWebSearch]], which made about:blank display advertisements.
{| class="wikitable"
! Address
! [[Internet Explorer]] (SP2)
|-
| '''about:DesktopItemNavigationFailure'''
| Displays "navigation cancelled" page.
|-
| '''about:Home'''
| Displays the user's home page.
|-
| '''about:NavigationCanceled'''
| Displays "navigation cancelled" page.
|-
| '''about:NavigationFailure'''
| Displays "navigation cancelled" page.
|-
| '''about:NoAdd-ons'''
| Displays information page when add-ons are disabled (IE7 only).
|-
| '''about:OfflineInformation'''
| Informs the user that the current page can not be viewed off line.
|-
| '''about:PostNotCached'''
| Informs the user that to refresh the current page, information entered in a form will have to be re-posted.
|-
| '''about:SecurityRisk'''
| Informs the user not to browse with the current security settings because they may be harmful to the computer.
|-
|}
In Internet Explorer 7, "about:Tabs" has also been included, and provides information about [[tabbed browsing]]. It is loaded when a new tab is created, if the "Open home page for new tabs instead of a blank page" option is selected, which is available under "Internet Options" > "General" tab > "Tabs" section > "Settings" button.
==Konqueror==
'''Note:''' Any "about:" URI except "about:blank" and "about:plugins" redirects to "about:konqueror".
{| class="wikitable"
! Address
! [[Konqueror]]
|-
| '''about:konqueror'''
| Shows a friendly 'start' and navigation page
|-
|}
==Epiphany==
Since [[Epiphany (browser)|Epiphany]] uses [[Gecko (layout engine)|Gecko]] as its layout engine, the [[#Common about: addresses|general]] and [[#Mozilla-specific about: addresses|Mozilla-specific]] <tt>about:</tt> addresses work as in [[Mozilla]] (or [[Mozilla Firefox]], depending on which branch of Gecko is used).
Additionally, <tt>about:epiphany</tt> yields a quote attributed to [[Antoine de Saint-Exupéry]]:
<div style="background: #3369FF; color: white; font-style: italic; padding: 2em 1em; margin: 0em 4em;">
<p style="margin-top: 1em; font-size: 1.3em; text-align: center;">
Il semble que la perfection soit atteinte non quand il n'y a plus rien à
ajouter, mais quand il n'y a plus rien à retrancher.
</p>
<p style="margin-top: 1em; font-size: 1.5em; text-align: right;">
<!-- Terre des Hommes, III: L'Avion, p. 60 -->
Antoine de Saint-Exupéry
</p>
</div>
Translated as: ''It seems that perfection is attained not when there remains nothing to add, but when there remains nothing to remove'', this can be seen as a rejoinder to critics who claim that the browser's (and the [[GNOME]] desktop's) focus on usability has led to a lack of features.
==Netscape (historic)==
*Older versions of the Netscape browser have an <tt>about:people</tt> URL that was similar to <tt>about:credits</tt> above, but it would redirect to Netscape's active employee listing. In addition, <tt>about:''username''</tt>, where ''username'' is the username of a Netscape employee, would redirect to the Netscape homepage of the employee specified. For example, <tt>about:jwz</tt> would redirect to '''<nowiki>http://people.netscape.com/jwz/</nowiki>''' (not an active link) [http://www.yikes.com/netscape/people.html] [http://www.jwz.org/gruntle/blowme.html].
*Not all employee pages were accessible through this scheme. Only developers that knew which file in the source tree and the encoding scheme used to obfuscate the directory of employee about entries could add their names.
*Many other about: easter eggs existed, including the famous about:mozilla, and other less known ones that showed pictures of the Netscape mascot Mozilla in various foreign garb, such as about:deutsche showing Mozilla in Lederhosen.
*Some versions of Netscape would display the browser history for the <tt>about:global</tt> address
==Safari==
'''Note:''' Any "about:" URI is accepted, but only a page with a blank source is returned, as with the "about:blank" of other browsers.
==Microsoft Outlook==
In [[Microsoft Outlook]], an additional [[Outlook URI Scheme | outlook:today]] URI was added, which showed the Outlook Today Screen (it shows messages, tasks and appointments). Also, although about:blank is supported, anything else (including about:about) typed after about: would show that text as a web page in the browser.
==External links==
*[http://kb.mozillazine.org/About_protocol_links About protocol links] in Mozilla and Mozilla Firefox.
*[http://lxr.mozilla.org/seamonkey/source/docshell/build/nsDocShellModule.cpp#138 about redirectors' source code] in firefox
==Notes and References==
# {{note|aboutblank}} The term "about:blank" is also the generic name for a group of variants of the [[CoolWebSearch]] [[malware]] program group.
{{URI scheme}}
[[Category:Web browsers]]
[[Category:Mozilla]]
[[Category:URI scheme]]
[[fr:About:]]
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[[ru:About: URI]]