How do I implement a single login interface for multiple providers in Azure AD B2C

Question

I have configured multiple external providers for Azure AD B2C. Right now, the user is forced to pick the provider that they want to authenticate with. How do I configure the system so that the user can type an email address, and the system can automatically forward the user to the proper IDP based on their email address. Similar to how the common authentication endpoint works for different azure domains in Azure AD work and student accounts.

Answer 1

Azure AD B2C does not provide any automatic IDP discovery functionality. You can request this feature in the Azure AD B2C feedback forum

You can implement this yourself by leveraging the domain_hint feature however this would require you keep your own table where you keep track of the username-to-IDP relationship. You'd then build your own page where the user can type his/her username, and based on this mapping table then redirect to B2C with the corresponding domain hint (for example, domain_hint=facebook.com)