The Facebook Platform provides a set of APIs and tools which enable third-party developers to integrate with the "open graph" — whether through applications on Facebook.com or external websites and devices. Launched on May 24, 2007, Facebook Platform has evolved from enabling development just on Facebook.com to one also supporting integration across the web and devices.

Facebook Platform statistics as of May 2010:

Third party companies provide application metrics, and several blogs have sprung up in response to the clamor for Facebook applications. On July 4, 2007, Altura Ventures announced the "Altura 1 Facebook Investment Fund," becoming the world's first Facebook-only venture capital firm.

On August 29, 2007, Facebook changed the way in which the popularity of applications is measured, to give attention to the more engaging applications, following criticism that ranking applications only by the number of people who had installed the application was giving an advantage to the highly viral, yet useless applications. Tech blog Valleywag has criticized Facebook Applications, labeling them a "cornucopia of uselessness." Others have called for limiting third-party applications so the Facebook user experience is not degraded.