WAYF (Where Are You From) is the connection between your login at Aarhus University (or another education institution) and external web services.
With WAYF you can use the standard AU-username (au, followed by your AUid, e.g. au123456) or AU-matriculation number as your username and the password you already have at mit.au.dk (Self-service). When you are logged on, you can switch between the various web services without a revalidation of the login.