I have a client that would like for users who sign up on a Wix site be able to sue their credentials on another (non Wix) site associated with their product (an app). Is this possible?
It isn’t - not via wix. Members are native to the site. There are a couple work arounds, though.
1: You can use social logins.
2: You can use a “SSO” with Wix (Single Sign On), where another third party actually authenticates the users on your site. This is a bit more complicated but completely doable. 
Hope this helps!
Thank you @brett , can you point me in the direction of any applicable resources, or recommend any particular SSO services?
@burkedunnweb [MemberSpace](MemberSpace
https://www.memberspace.com/?via=certifiedcode)
@wingcc Thank you so much, I’ll check them out!