The Browser Compatibility API was a project to support compatibility data on the Mozilla Developer Network. This currently takes the form of browser compatibility tables, such as the one on the CSS display property page. The API would centralize this data, and allow it to be kept consistent across languages and presentations.
The project started in December 2013. The initial goals and requirements are documented on the MozillaWiki.
This project has been cancelled. The have been no code changes since March 2016. In April 2017, we started the process of removing integration from MDN and decommisioning the API server. See the issues page for the status as of March 2016.
As of 2017, these are the current MDN data projects: