Mozilla Firefox is a free and open-source web browser developed by Mozilla Foundation and its subsidiary, Mozilla Corporation. Firefox is available for Windows, macOS, Linux, and BSD operating systems. Its sibling, Firefox for Android, is available for Android. Firefox uses the Gecko layout engine to render web pages, which implements current and anticipated web standards. In 2016, Firefox began incorporating new technology under the code name Quantum to promote parallelism and a more intuitive user interface. An additional version, Firefox for iOS, was released in late 2015; due to platform restrictions, it uses the WebKit layout engine instead of Gecko, as with all other iOS web browsers.