I've spent a whole afternoon looking for real world examples of SSO logins which work without redirects or pop-ups - and had no luck.

Does this mean they do not exist or do I just suck at searching?

I want to be able to login from blabla.com to blablablablabla.com as well - without redirects or popups. I am looking for real examples not instructions how to pull it off.

Thanks so much.