Check user IP is a tool that lets you see which accounts have been used by a given IP address. It can help identify people who are abusing the community by using multiple accounts, or who are engaged in vandalism and spam.
The check user IP uses a database table that contains information about all edits to English Wikipedia made from a given IP address or range, and the list of accounts that use that IP. This table is updated in real time whenever someone makes a change to the page that CheckUser is investigating. The information in this table is private and will not be shown to other users of the wiki. Only the person who has been checked and their authorized agents will have access to this data.
Why IP Lookup Tools Are Essential for Online Security
It is possible to discover an IP address using a command line program such as the ‘whois’ or ‘nslookup’ commands (on Unix systems, type whois [IP address] at the terminal; on Windows, try All Net Tools). This will usually give you the fully qualified domain name (FQDN) associated with that IP, which can be used to determine the name of the owner or operator.
Note that this technique is often referred to as “fishing” and is considered inappropriate except when there is reasonable suspicion of abusive sockpuppetry. In some cases, checking the same account from multiple different IPs can result in a false positive; for example, if one user is using an anonymous IP to create a large number of edits on many different pages.