Evolving from the well-known Kindle series of e-readers, Amazon.com created an independent branch, or fork, of the Android platform using its open-source code. The system would then be modified to tie into the company's retail platform. Early versions were simply referred to as Kindle Fire system software based on Android, but the platform was renamed Fire OS with the third-generation tablets and beyond. The Fire HDX series of tablets was the first to use the software under its present name. Being a fork of Android, Fire devices can run Android apps, provided that an app does not make explicit requests to Google Play and meets certain other criteria. The current major version is Fire OS 5, released in 2015.