API authentication

Decoupling brings about a few more challenges when it comes to authentication and authorization. It's not uncommon to have an API that does not require authentication, but the chances are some web services you'll encounter will require their clients to authenticate in one way or another.

So, how do we achieve authentication with APIs? This process is not that different from a typical application. At its core, authentication requires that you provide something you know and, optionally, something you have, which corresponds to a record in the API's database. If that something you know and something you have is a secret and only the holder of this information, presumably, has access to it, the API can be reasonably sure that the client providing this information is given access. The API now only needs to track this particular client, since HTTP is stateless.

Traditional web applications will accept authentication data (something you know, along with a username and password...