Google Account Authentication The ClientLogin API lets you incorporate programmatic login into desktop or mobile applications, while the AuthSub API gives web applications the ability to access a user's Google account without handling the user's login information. The Google data APIs ("GData" for short) provide a simple standard protocol for reading and writing data on the web. GData combines common XML-based syndication formats (Atom and RSS) with a feed-publishing system based on the Atom publishing protocol, plus some extensions for handling queries.