Version 3 of the WhatIsMyBrowser.com Browser Detection API is available now.
Documentation for Version 2 of the API. Version 2 is no longer the latest version of the API, but there are some API endpoints which might still be useful to you - namely, for the User Agent Parsing and Searching features.
Documentation for Version 1 of the API. Version 1 is deprecated; it still works, but you are missing out on features by still using it.