[dec0dedab0de]

They could just check if the username needs to be redirected, and if they do then ignore the password. It wouldn't be that hard.

The only downside is the user submitting a password they dont need to, but if you're using js you could post the username first and only post the password if needed. That would be the same exact process, except from the users perspective it would be seamless. You could even have it check the username as they type, and lock the password field if its not needed.

[notatoad]

this is exactly the sort of thought process that leads to terrible login flows. yes, it's technically possible, and it works for you.

but the login flow is one area of your product that needs to work for everybody. There's plenty of features that can be tailored to a power-user workflow because they're the only people that will see it, but the sign-in flow is not one of those. any confusing UI in your sign-in flow is going to confuse your least-confident users. and asking people using Facebook Sign-in to enter a password when they haven't ever set a password for your site is extremely confusing. all just to save a couple keystrokes for the most-technically-competent users.

[dec0dedab0de]

Well for facebook, and any other big ones they could just click "sign in with facebook" thats common enough.

The problem is when you have a bunch of enterprise customers and you're not sure which custom login to use, and you dont want to list all your clients.

Ideally, this is solved by the client company telling its employees to use an internal link that authenticates and redirects. Though I'm sure not all clients are capable of this, and still want to use SSO. In that case, I think my solution is much nicer than requiring a two step login.

[scarface74]

I could see a lot of large companies that integrate with other B2B sites recoil in horror with a UI that encourages employees to enter their corporate email address and a password. Many employees would use their corporate passwords.