From mediawiki.org
MediaWiki extensions manual
OOjs UI icon advanced-invert.svg
Release status: stable
Implementation Special page , User identity , API , Hook , Database
Description CheckUser function allows a user with permissions to check which IPs are used by a given username and which usernames are used by a given IP, without having to run queries directly against the database by hand.
Author(s) Tim Starling, Aaron Schulz
Latest version 2.5 (continuous updates)
Compatibility policy Snapshots releases along with MediaWiki. Master is not backward compatible.
MediaWiki 1.27+
PHP 5.4+
Database changes Yes
Tables cu_changes
License GNU General Public License 2.0 or later
  • $wgCheckUserGBtoollink
  • $wgCheckUserCAMultiLock
  • $wgCheckUserLogSuccessfulBotLogins
  • $wgCheckUserLogLogins
  • $wgCUPublicKey
  • $wgCheckUserCAtoollink
  • $wgCUDMaxAge
  • $wgCheckUserCIDRLimit
  • $wgCheckUserMaxBlocks
  • $wgCheckUserCommentMigrationStage
  • $wgCheckUserForceSummary
  • $wgCheckUserEnableSpecialInvestigate
  • $wgCheckUserLogAdditionalRights
  • $wgCheckUserInvestigateMaximumRowCount
  • $wgCheckUserTemporaryAccountMaxAge
  • $wgCheckUserEventTablesMigrationStage
  • $wgCheckUserMaximumRowCount

  • checkuser
  • checkuser-log
  • investigate
Quarterly downloads 268 (Ranked 39th)
Public wikis using 4,936 (Ranked 20th)
Translate the CheckUser extension if it is available at translatewiki.net
Issues Open tasks · Report a bug
This page is about the extension itself. For the Wikimedia Foundation CheckUser policy, see m:CheckUser policy.

CheckUser is an extension that allows a user (with the checkuser permission) to check which IP addresses are used by a given username and which usernames are used by a given IP, without having to run queries directly against the database by hand. The extension is running live on all Wikimedia wikis.


The extension can be retrieved directly from Git [?]:

  • Browse code
  • Some extensions have tags for stable releases.
  • Each branch is associated with a past MediaWiki release. There is also a "master" branch containing the latest alpha version (might require an alpha version of MediaWiki).

Extract the snapshot and place it in the extensions/CheckUser/ directory of your MediaWiki installation.

If you are familiar with Git and have shell access to your server, you can also obtain the extension as follows:

cd extensions/ git clone https://gerrit.wikimedia.org/r/mediawiki/extensions/CheckUser.git


The extension is released under the GNU General Public License 2.0 or later. The software is provided as-is. Updates will be made according to the needs of Wikimedia wikis; or where critical vulnerabilities are discovered.

On an existing wiki


  • If you have installed other extensions without running php maintenance/update.php, run that first.
  • Download and place the file(s) in a directory called CheckUser in your extensions/ folder.
  • Only when installing from Git, run Composer to install PHP dependencies, by issuing composer install --no-dev in the extension directory. (See task T173141 for potential complications.)
  • Add the following code at the bottom of your LocalSettings.php :
    wfLoadExtension( 'CheckUser' );
  • Run the update script which will automatically create the necessary database tables that this extension needs.
  • Configure as required.
  • Yes Done – Navigate to Special:Version on your wiki to verify that the extension is successfully installed.

When installing from Git, please note that this extension requires Composer .

So, after installation from Git change to the directory containing the extension e.g. "../extensions/CheckUser/" and run composer install --no-dev, or when updating: composer update --no-dev.

Alternatively as well as preferably add the line "extensions/CheckUser/composer.json" to the "composer.local.json" file in the root directory of your wiki like e.g.

	"extra": {
		"merge-plugin": {
			"include": [
Installing without command prompt access

Many hosting providers don't allow direct shell access, but allow creation of cron jobs (e.g. via cPanel web interface). For those hosting providers a temporary cron job can be used to run php /path/to/install.php (naturally /path/to should be replaced with real full path to install.php). If you are using a remote server and do not have command prompt access (nor cron job solution is suitable for you), but do have access through phpMyAdmin, substitute these steps for step #2 above:

  1. Choose and download the tables_generated.sql file from the CheckUser/schema folder. Navigate in to the folder of the DB you are running to find the files.
  2. In phpMyAdmin, click the database you're using for MediaWiki along the left side
  3. On the next screen, click the "Import" tab at the top.
  4. At "Location of the text file", choose one of the files, select compression "None", and click the bottom "Go" button.
    If your phpMyAdmin screen has only a text field and no text file chooser, click the "SQL" button in the left-side column, under the phpMyAdmin logo, and click the "import files" tab in the new window that opens.
  5. Repeat for the second file

On a new wiki

Follow step 1 as above, then run the MediaWiki installation. The MediaWiki installer will automatically perform the installation tasks if you select the checkbox for CheckUser when prompted for which extensions to install.

Using Mediawiki-Docker

Follow the steps in MediaWiki-Docker/Extension/CheckUser to install this extension inside a MediaWiki Docker instance.


This tool migrates recent changes data to a separate tables, and adds to that when new entries are added. If $wgPutIPinRC was previously set to false, there will be no initial data to search but new edits will fill in as soon as the extension is set up.

After you run the queries, you can reduce $wgRCMaxAge to make recentchanges shorter, without affecting checkuser. Use $wgCUDMaxAge to set how far back checkuser data can go, in seconds.

The CheckUser-specific setting $wgCheckUserCIDRLimit determines the largest range that can be checked in a single check. Its format is the same as $wgBlockCIDRLimit . The default limit is /32 for IPv6 checks and /16 for IPv4 checks.

To enable Special:Investigate, set $wgCheckUserEnableSpecialInvestigate to true in LocalSettings.php.

Granting right to use CheckUser

To grant the right to use the Check User function, a user with user rights management must go to Special:UserRights and enter the user's name in the box, then select the option "checkuser". Once this is done, Special:CheckUser and Special:CheckUserLog will show up in Special:SpecialPages page for that user.

To turn on user rights management for sysops, put the following into LocalSettings.php:

$wgGroupPermissions['sysop']['checkuser'] = true;
$wgGroupPermissions['sysop']['checkuser-log'] = true;
$wgGroupPermissions['sysop']['investigate'] = true;

To only allow the adding and removing of the checkuser permission, use the following instead:

$wgAddGroups['sysop'][] = 'checkuser';
$wgRemoveGroups['sysop'][] = 'checkuser';


Configuration settings in extension.json
parameter default comment
$wgCUDMaxAge 7776000 How long to keep CU data (in seconds)? (default = 3 months)
$wgCheckUserMaxBlocks 200 Mass block limits
$wgCheckUserForceSummary false Set this to true if you want to force checkusers into giving a reason for each check they do through Special:CheckUser. (Not very useful, given that checkusers could simply give a summary such as "they need to be checked" or "I feel like it" and the software would not know.)
$wgCheckUserCIDRLimit [ 'IPv4' => 16, 'IPv6' => 32 ] Shortest CIDR limits that can be checked in any individual range check
$wgCUPublicKey '' Public key to encrypt private data that may need to be read later. Generate a public key with something like:

openssl genrsa -out cu.key 2048; openssl rsa -in cu.key -pubout > cu.pub and paste the contents of cu.pub here

$wgCheckUserCAMultiLock false This can be used to add a link to Special:MultiLock by CentralAuth to the Special:CheckUser's mass block form. This requires the CentralAuth extension to be installed on the wiki. To enable this, set this to an array with a central wiki's database name and an array with the name(s) of the global group(s) to add the link for. For example:
$wgCheckUserCAMultiLock = [
    'centralDB' => 'metawiki',
    'groups' => [ 'steward' ]
$wgCheckUserCAtoollink false Since 77360f1cf1d2. This adds a link to central wiki Special:CentralAuth to the Special:CheckUser's "Get users" results. This requires the CentralAuth extension to be installed on the wiki. To enable this, set this with a central wiki's database name. For example:
$wgCheckUserCAtoollink = 'metawiki';
$wgCheckUserGBtoollink false Since 77360f1cf1d2. This adds a link to local or central wiki Special:GlobalBlock to the Special:CheckUser's "Get users" results. This requires the GlobalBlocking extension to be installed on the wiki. To enable this, if a $wgConf is configured, set this to an array with a central wiki's database name and an array with the name(s) of the local (or global if you have CentralAuth installed) group(s) to add the link for. For example:
$wgCheckUserGBtoollink = [
	'centralDB' => 'metawiki',
	'groups' => [ 'steward', 'staff' ]
$wgCheckUserEnableSpecialInvestigate false Since 57dcfe46d2e4. This enables Special:Investigate, an updated version of Special:CheckUser that allows checking for multiple user accounts and IP addresses within one investigation.
$wgCUPublicKey '' Used with an associated private key to encrypt certain data that is not shown to CUs but stored in the cu_changes or cu_private_event table. Currently this is only the recipients of emails. Without a valid public key the data will not be stored.
$wgCheckUserLogLogins false Whether CheckUser should log login attempts (both successful and not) in the checkUser table.
$wgCheckUserLogSuccessfulBotLogins true Whether CheckUser should store successful login attempts to accounts with the bot user group if $wgCheckUserLogLogins is set to true. Only is used if $wgCheckUserLogLogins is true
$wgCheckUserMaximumRowCount 5000 The maximum number of results that can be returned by Special:CheckUser. Before MediaWiki 1.39, in the 'Get edits' and 'Get IPs' results having over 5000 results would return the results in a different format. From MediaWiki 1.39 this is the maximum number of results to show by page and more can be generated using the paging links
$wgCheckUserInvestigateMaximumRowCount 25000 Similar to $wgCheckUserMaximumRowCount, but for Investigate

Special:CheckUser usage

Basic interface

  1. Go to Special:CheckUser.
  2. In the user field, type in the username (without the User: prefix), IP address, or CIDR range.
    • IP: any IPv4 or IPv6 address.
    • CIDR: you can check a range of IP addresses by appending the CIDR prefix (by default, up to /16 for IPv4 (65,536 addresses), up to /64 for IPv6 (~1.8446*1019 addresses) before gerrit:7352, up to /48 for IPv6 (~1.2089*1024 addresses or 65536 /64s - controlled by $wgCheckUserCIDRLimit in the latest version) after revision 7352, and up to /32 (65536 /48's) after phab:rECHU9d7c239bf88866eca577f3241194d440f94fa014). For notation, see Help:Range blocks .
    • XFF: you can check a client IP address provided by X-Forwarded-For headers by appending /xff (for example,
  3. Select the information you want to retrieve.
    • Get IP addresses - returns IP addresses used by a registered user.
    • Get edits - returns all edits and logged actions made by users using an IP address or range specified in the target field, or if the target is a user all edits and logged actions by that user.
    • Get users - returns user accounts that have edited from an IP or range.
  4. In the "Reason:" field, type in the reason you are accessing the confidential data. Try to succinctly summarise the situation (for example, "cross-wiki spam"); this will be logged in a log visible only to users with the checkuser-log permission.

Information returned

A typical entry in the CheckUser results for a user summary ("get users") is as follows:

  1. Example user agent

This is formatted to fit a lot of information into a format that can very easily be listed and skimmed, but is difficult to read unless you know what the information provided is. The information is laid out as follows:

  • username (user links) (time period when they edited from the given IP or range) [number of edits from the IP or range]
    1. IP address edited from XFF: XFF information provided (can be spoofed)

Each IP/XFF combination used to edit is listed, in order of use.

The last ten user agents (browser, operating system, system language, and versions) for each user for edits made in the IP or range are listed afterwards.

XFF Format

XFF (X-Forwarded-For) headers indicate the series of IP addresses used from the user's computer (first) to the last proxy server. In case of Wikimedia, the last proxy server is one of the Wikimedia proxies (listed under $wgCdnServersNoPurge in the Wikimedia configuration file).

In this example:

aaa.aaa.aaa.aaa XFF:,, aaa.aaa.aaa.aaa,

  • the first two addresses (, are private to the originating network and can't be reached directly from the public Internet,
  • the third address (aaa.aaa.aaa.aaa) is the "public face" of the editor, usually a broadband or dial-up ISP, a company gateway, (but possibly an anonymizer or a malware-compromised server),
  • the last address ( is one of the Wikimedia squids (sq36.wikimedia.org).

MediaWiki configuration settings $wgUsePrivateIPs , $wgCdnServers , $wgCdnServersNoPurge and extensions using the IsTrustedProxy hook (such as Extension:TrustedXFF ) change the way an actual IP address used to attribute edits is selected.

Personal tool links

When you get results from Special:CheckUser you can add personal user tool links via two interface messages:

Special:Investigate usage

Basic usage

  1. Go to Special:Investigate.
  2. In the Usernames and IP addresses field, type in up to 10 targets, which may be usernames (without the User: prefix), IP addresses, or CIDR ranges.
  3. In the Reason field, enter the reason you are accessing the confidential data, as described in the Special:CheckUser instructions above; this will be logged in a log visible only to users with the investigate permission.

For advanced feature usage, see Help:Special Investigate.

Customizing tool links

As with Special:CheckUser, links to external tools can be customized.

The links are defined in the checkuser-investigate-compare-toollinks message. This message is parsed to find links, which are added to the menu in the IPs and user agents tab.


CheckUser also provides an API.