When you’re constructing a service that is intended for a base of users or provides a mechanism for giving people privileged access to certain resources, the issue of authenticating (allowing users to log in) naturally comes up.

Building an entire membership system and login infrastructure for this task can seem daunting, but it doesn’t need to be. OpenID allows a website or service owner to quickly integrate a login system that builds off many of the top membership systems currently in use and is a great alternative to a traditional, home-brewed model.

This chapter will focus on OpenID’s core features, covering examples and methods to show you how to leverage this standard to quickly integrate a user authentication system.