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.|
|License||GNU General Public License 2.0 or later|
|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 [?]:
- Some extensions have tags for stable releases.
- Select the tag
- Click "snapshot"
- 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).
- Browse branches
- Select a branch name
- Click "Continue"
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:
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
- Add the following code at the bottom of your
wfLoadExtension( 'CheckUser' );
- Run the update script which will automatically create the necessary database tables that this extension needs.
- Done – Navigate to Special:Version on your wiki to verify that the extension is successfully installed.
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
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:
- Choose and download the relevant cu_changes.sql and cu_log.sql files from the CheckUser/schema folder. Navigate in to the folder of the DB you are running to find the files.
- In phpMyAdmin, click the database you're using for MediaWiki along the left side
- On the next screen, click the "Import" tab at the top.
- 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.
- 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.
This tool migrates recent changes data to a separate
cu_changes table, and adds to that when new entries are added.
$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.
$wgCUDMaxAge to set how far back checkuser data can go, in seconds.
In versions for MediaWiki 1.22 and later, the CheckUser-specific setting $wgCheckUserCIDRLimit determines the largest range that can be checked in a single check.
Its format is the same as $wgBlockCIDRLimit.
Otherwise, the default limit (for all versions) is
IPv6 checks and
To enable Special:Investigate, set
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
$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';
||How long to keep CU data (in seconds)? (default = 3 months)|
||Mass block limits|
||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.)|
||Shortest CIDR limits that can be checked in any individual range check|
||Public key to encrypt private data that may need to be read later. Generate a public key with something like:
||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' ] ];
||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';
||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' ] ];
||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.|
||Used with an associated private key to encrypt certain data that is not shown to CUs but stored in the cu_changes table. Currently this is only the recipients of emails. Without a valid public key the data will not be stored.|
||Whether CheckUser should log login attempts (both successful and not) in the checkUser table.|
||Whether CheckUser should store successful login attempts to accounts with the bot user group if $wgCheckUserLogLogins is set to |
||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|
||Similar to $wgCheckUserMaximumRowCount, but for Investigate|
- Go to Special:CheckUser.
- 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 Range blocks.
- XFF: you can check a client IP address provided by X-Forwarded-For headers by appending
- 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.
- 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
Basic CheckUser interface
Example username check
Example IP check
Example Get edits check
A typical entry in the CheckUser results for a user summary ("get users") is as follows:
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:
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 (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:
- the first two addresses (
127.0.0.1) 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 (
188.8.131.52) is one of the Wikimedia squids (
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.
When you get results from Special:CheckUser you can add personal user tool links via two interface messages:
MediaWiki:checkuser-userlinks-ipfor IP addresses (for example m:MediaWiki:checkuser-userlinks-ip)
MediaWiki:Checkuser-userlinksfor registered users (for example m:MediaWiki:Checkuser-userlinks)
MediaWiki:checkuser-toollinks- for IPs in the 'Get IP Addresses' check type (for example m:MediaWiki:checkuser-toollinks)
- Go to Special:Investigate.
- 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.
- 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.
Account information tab
IPs and user agents tab
For advanced feature usage, see Help:Special Investigate.
As with Special:CheckUser, links to external tools can be customized.
The links are defined in the
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.
|This extension is being used on one or more Wikimedia projects. This probably means that the extension is stable and works well enough to be used by such high-traffic websites. Look for this extension's name in Wikimedia's CommonSettings.php and InitialiseSettings.php configuration files to see where it's installed. A full list of the extensions installed on a particular wiki can be seen on the wiki's Special:Version page.|
|This extension is included in the following packages and/or wiki farms:|