Extension:Campaigns

Via a simple URL parameter, the campaigns extension logs a unique identifier associated with an account creation event. The purpose of a campaign is to differentiate the source of an account registration, such as a CentralNotice banner, email, or template on a wiki.

How it works
When a user follows a URL to the "Create account" form with ?campaign=foo in it, Extension:Campaigns stores the campaign identifier in a session cookie (if the user is not logged-in already). If and when the user successfully creates an account during their session, the campaign is logged, along with the userid and other data collected via Schema:ServerSideAccountCreation.

Any campaign identifier attached to an account creation URL will be logged, so choose wisely. If you reuse a campaign identifier or pick something too generic, this increases the chance you will not be able to ascertain which registrations were actually associated with your campaign. The only limit is that it cannot be longer than 40 characters. Never include personally-identifiable information in a campaign parameter.