When I enable single sign-on, what happens to existing users and their accounts?

Question

As a Zendesk administrator, when I enable single sign-on on my account, what affect does this have on existing users? 

Answer 

What happens to existing users depends on what email address is listed on their Zendesk profile. If the primary email address on the existing user's profile is the same as their email in the single sign-on system, the user will have no trouble logging in and accessing their profile.

If the primary email address on the current user's profile is different from their email in the single sign-on system, a new user profile is created for their new email address.

For more detail on this process, see these articles: Enabling social and business single sign-on and Enabling JWT (JSON Web Token) single sign-on.

If you do find a duplicate account is accidentally created for an existing user, you can always merge the two profiles together as described in this article: Merging a user's duplicate account.

Note: If you choose to keep Zendesk Authentication enabled as well, your existing users will be able to use their previous login email and password as a fall back as well. For more information on this option, see this article: Accessing your Zendesk account when your SSO service is down