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. A source you identify via a URL parameter is called a campaign, since it can help you learn if a particular source you're interested in is effective at driving new registrations.

How it works
When a user follows a URL to the "Create account" form with   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 with the data collected via Schema:ServerSideAccountCreation.

See Engineering subpage for some background.

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.