As part of Harvard’s “one identity for life” paradigm, your HarvardKey password automatically replaces your HUID password so you don’t have to remember extra credentials. While your HarvardKey login name and password will get you access to all the applications and resources as your HUID, if you ever need to log in to an app or service using your HUID as the login name, simply use the password associated with your HarvardKey.
If you're ever confused about which login type gets you into which application at Harvard, you may want to check this...
Read more about I have a HUID, but after I claimed my HarvardKey, my HUID password doesn’t work. Why?