OAuth is an open protocol to allow secure API authorization in a simple and standard method for desktop, mobile and web applications.
For consumer developers, OAuth is a method to publish and interact with protected data. For service provider developers, OAuth gives users access to their data while protecting their account credentials. In other words, OAuth allows a user to grant access to their information on one site (the Service Provider), to another site (called Consumer), without sharing all of his or her identity.
OAuth Core 1.0, the main protocol, is stable and ready to be implemented. Libraries are already available for many popular platforms such as PHP, Rails, Python, .NET, C, and Perl.