During this era, all major web browsers implemented support for HTML5 video. Supported codecs, however, varied from browser to browser. Current versions of Android, Chrome, and Firefox support Theora, H.264, and the VP8 version of WebM. Older versions of Firefox omitted H.264 due to it being a proprietary codec, but it was made available beginning in version 17 for Android and version 20 for Windows. Internet Explorer and Safari support H.264 exclusively, but the Theora and VP8 codecs can be manually installed on the desktop versions. Given the popularity of WebKit for mobile browsers, Opera Software discontinued its own Presto engine in February 2013. The Opera 12 series of browsers were the last to use Presto with its successors using WebKit instead. In 2015, Microsoft discontinued production of newer versions of Internet Explorer. By this point Chrome overtook all other browsers as the browser with the highest usage share.