Source: /cirosantilli/oauth

= OAuth
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{wiki}

The fatal flaw of OAuth is that websites have to enable specific providers, they can't just automatically select the correct OAuth for a given email domain. This means that the vast majority of websites will only provide the most widely popular providers such as <Google>, and the like, which means people won't have decent privacy.

So you are just better off with password logins and a decent <password manager>.