What is an inactive user?

Sometimes, when trying to add a Trello user to your board or team, you may see their account labeled as inactive:

We'll label users as inactive if they haven't logged in to Trello for 90 days. Their accounts still remain in Trello, and they can log in to them at any time (at which point we'll remove the fading and the note for users who try to add them to their boards or teams).

If you're trying to add a colleague to a board or team and see them labeled as not having logged in recently, double-check that you've got the right user by asking your colleague for their username, or inviting them via email address.