Research:Registration

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A user registration is the act of creating a new user account on a Wikimedia project. The registration timestamp is stored in the database as user.user_registration. However, in MediaWiki's early years, the system did not record the timestamp at all; some rows have had the value backfilled based on the user's first edit using a maintenance script, but in others it remains NULL. Fully populating the field has long been discussed in T24097.