Imagine I’ve created a website that provides two OAuth options: Google and Telegram.

You simply click “Login with Google” or “Login with Telegram” and your new account is created just like that.

The issue is that Google gives you user’s email (that’s how you verify theirs identify) but Telegram gives you, say, their phone number. That means the using these two buttons will essentialy create two different accounts, which is unideal to say the least.

And then, while inside your account, you should be able to “link” either a Google account or a Telegram account to your website account (so that loging with Telegrams account T, which is linked to website account W, will log you in into W). But how would you then merge these two accounts?

How do websites usually deal with all of this?