# OAuth

OAuth is an [authorization](/glossary/a/authorization) method used to provide access to resources over HTTP/S. It works by providing access tokens representing a user permissions to access a resource. This token is used by a client to [authenticate](/glossary/a/authentication) its requests.

There are two versions of OAuth: *OAuth 1* which uses an HMAC-SHA signature strings, and *OAuth 2* (using tokens over [HTTPS](/glossary/h/https).