I came across this question in a closed LinkedIn group. I think it's a great one and since it's hidden from search engines, I decided to bring it to the outside world.
Some users don't visit your website/application as frequently as others and are bound to forget their login credentials. When accounts are created with a simple username-password combo, you offer the
Forgot your login details? option.
However, what do you do when you also use 3rd-party authentication APIs (e.g. OAuth or OpenID)?
- What is the most effective way to help returning users remember the service they used to create their accounts?
- How do you prevent them from creating a duplicate account via another authentication service?
I realize the answer might be more technical than design and might have include some back-end code. If that's the case, please simply link to the documentation and don't post the code here.