Today’s API are used for a variety of things such as passing data to another webservice, reading data from a database etc. The problem with this is that not all the API`s are secure. Most of the todays API are old and rely only on an authentication token or string which is often hardcoded. We will focus on OAUTH 2.0 as a new protocol in securing our API`s. This is a new protocol based on delegation of authorization, dynamically changing authentication string based on user session or application session. We will go on this different modes of authentication and show you how to use them properly. We will set up this with a Web Api integrated with OAUTH and a client application that will stimulate the requests to our API.