User:0

Although the user 0 is a real editor (not a bot), the edits originally attributed to that username from 2002 were made by several Wikipedia users. This is due to a bug in a very early version of MediaWiki, then known as the Phase III Software, where if a user made an edit some time between 20 and 24 July 2002, all the previous edits to that page by registered users (including those by Conversion script) would be re-attributed to User:0, and all the edits by anonymous users would have their IP addresses truncated (for example, see the contributions of User:11.105). There is some more information about this issue in the old SourceForge bug reports system in bug numbers 158 and 165. The truncation is reported as T106941.

Edits made before 25 January 2002, during the UseModWiki era of Wikipedia, were imported in September 2002, so were unaffected by this bug. In the case of registered users who had their edits attributed to this username, the editors' user ID's were preserved, so those with non-zero user ID's were re-assigned to the correct usernames during the database "actor migration" in 2019; most of the remaining edits were by Conversion script. In the list of Wikipedians by number of edits until March 2004, this username had 1,920 edits attributed to it.