Its unofficial ports are available for various Unix and Unix-like operating systems including FreeBSD,[7] OpenBSD,[8] NetBSD,[9] illumos,[10] and Solaris Unix.[12] Firefox is also available for Android and iOS. However, the iOS version uses the WebKit layout engine instead of Gecko due to platform requirements, as with all other iOS web browsers. An optimized version of Firefox is also available on the Amazon Fire TV, as one of the two main browsers available with Amazon's Silk Browser.[25]