Update: we have recently migrated code projects to GitHub and the links in the table below now point to new locations. 
If you’re not using 
OAuth2 , this blog post is aimed at you. OAuth2 is the preferred authorization mechanism at Google. That’s mainly because it’s simpler and easier to use than OAuth1 but also because it’s a lot safer than Client Login. In addition, if you’re still using Client Login you should be aware it’s 
deprecated .
The following video shows what you need to get started with OAuth2 for Ads. It explains what OAuth2 is, how it works, how to use it with our APIs, the different flows of OAuth2 and some best practices. If you just need the client library resources to get started, skip ahead to the Client Libraries section to get all the resources you’ll need to make the switch.
VIDEO 
After watching the video you will understand:
OAuth2: 
The Authorization mechanism 
 
Better than Client Login: 
OAuth2 is more secure 
More specific access control 
No CAPTCHA challenges 
 
Using OAuth2: 
Registering your application 
Making the authentication requests 
Where OAuth2 tokens fit into regular service calls 
 
Implementing OAuth2: 
Authorization Flows: 
Best Practices: 
 
With that knowledge, updating your applications to use OAuth2 should be trivial. All the 
client libraries  have comprehensive support for OAuth2 and helpful examples to demonstrate its use. For further information on configuring OAuth2 in any of the libraries, see the table below.
Client Library OAuth2 Resources