Earlier quoted context omitted.
That's because web developers are not great at sticking to conventions and standards for this stuff. Product owners and UX designers seem to ignore aligning their signup and signin UX with obvious requirements for enabling people to use a password manager. If they'd make this a hard requirement, it would happen. It's not that hard even; we did that for our login form. Works great with Bitwarden. And on mobile too. Bu…
> Splitting the email and password form across two screens. This is done because it's an easier way to support both local login and SSO(like oauth or saml). By taking the username first you can determine whether to ask them for a password or send them to a sso provider. It doesn't have to be implemented this way but it is seen as easier.
Also, a typical opendid flow or SSO would not actually require an email field at all. So splitting the screens is kind of redundant in that case. E.g. a Github signin would be done with a button click and a few redirects.