0 was the first version of OAuth and is now deprecated. It was created in 2007 by Parecki, Evan Rose, and Christopher Allen at a time when Facebook had just launched its API but did not support any authentication mechanism other than username/password. The goal of OAuth 1.0 was to provide an open standard for delegated access to resources on behalf of users without requiring passwords or usernames that could be used elsewhere (the so-called “single sign-on”).

OAuth 2
https://t.co/rjvZGRYO8i