I was enthusiastic about OpenID when it came out. I actually had been idly building an almost identical thing (proof of concept stage, but it wasn't sure how to

I was enthusiastic about OpenID when it came out. I actually had been idly building an almost identical thing (proof of concept stage, but it wasn't sure how to get the needed widespread adoption so didn't pursue it much further) but stopped once I found OpenID. What I really liked was you could login with your own IdP, so for example you typed in "yourdomain.com" and got redirected to authenticate (no interaction if you already had a live session on your IdP). You could enable this with an html meta tag, even if you didn't run the actual provider. Unfortunately the only big site I used that had it was stack overflow. I haven't followed as closely but I don't think OpenID Connect (which is based on oath2) even allows this; instead it only works with the providers the site operator has decided to enable it for. Which of course are typically just the big ones.