This tool scans recent changes to retrieve the IP addresses used by a user or show the edit/user data for an IP address. Users and edits by a client IP address can be retrieved via XFF headers by appending the IP address with "/xff". IPv4 (CIDR 16-32) and IPv6 (CIDR 96-128) are supported. No more than 5,000 edits will be returned for performance reasons. Use this in accordance with policy.
MediaWiki:Checkuser-summary
From Card Hunter Wiki