This page contains technical documentation relating to change tags; its content is aimed at MediaWiki extension developers.
For help and documentation aimed at users and administrators, please see Help:Tags.
Change tags or revision tags are annotations associated with a revision or log entry. They are displayed in various locations when referring to revisions, such as in the page history, diffs, recent changes and other places.
A complete list of all the available tags is displayed on Special:Tags. Users with the
managechangetags user right – administrators by default – can use this special page to create and delete tags (see Help:Tags).
If you are planning to hard-code tags into your extension, pick a somewhat unique name to avoid conflicts. For example, VisualEditor uses
visualeditor-switched. Tag names may not contain
, (comma) or
/ (forward slash) characters.
If your extension allows users to enter their own tag names, you can use the
ChangeTags::canCreateTag( $tag ) function to validate those names. (There is no need to pass the optional
$user parameter for this purpose.) This function will reject invalid tag names, as well as tag names that are already reserved by another extension or by users on the wiki.
Make sure to register all tags your extension uses (whether hard-coded or user-supplied) by implementing the
ListDefinedTags hook. If a tag is in active use (that is, it is not disabled), you should also list it via the
If you wish to prevent users from creating certain tags, you can implement the
ChangeTagCanCreate hook. For example, the OAuth extension uses this hook to reserve all tags beginning with
OAuth CID: (see source).
Each tag is known by a code name, which functions as its unique identifier. This code name is displayed on Special:Tags. Two messages are associated with each tag:
MediaWiki:tag-$namecan be used to set the "display name" or "friendly name" of the tag. If set, this message will be used on history pages etc. instead of the tag's code name.
MediaWiki:tag-$name-descriptionprovides a description to be displayed on Special:Tags.
To add a tag to a revision, recent changes entry, or log entry, use
RecentChange_save hook can be useful for this purpose.
By default, tags defined by extensions cannot be manipulated from Special:Tags at all. All tag management tasks are left up to the extension.
If you wish, you can allow users to delete a tag defined by your extension from the regular Special:Tags interface. To do this, you must implement the
ChangeTagCanDelete hook to mark the tag as deleteable, then implement the
ChangeTagAfterDelete hook to perform extension-specific cleanup actions after MediaWiki has removed the tag from all revisions and log entries to which it is applied.