The Windows 10 Anniversary Update, due this summer, will expand the range of video and audio codecs that are supported by the Edge browser. Microsoft is adding the VP9 video codec, the Opus audio codec, and the WebM container format.

VP9 and WebM are both spearheaded by Google. Google bought video codec company On2 in 2010 with the intent of opening up On2's VP8 codec to serve as an open source, royalty-free alternative to the open but royalty-incurring H.264. Unfortunately, groups claiming to have patents that covered VP8 emerged. Google ultimately came to an agreement with those groups in 2013 to ensure the codec's royalty-free status, but by then, H.264 was too firmly entrenched to displace.

VP9 is a successor to VP8 that is more efficient and essential for the growing demand for 4K video. Along with Microsoft and others, Google has joined the Alliance for Open Media to promote VP9's development and try to ensure that it remains royalty-free. As with VP8 before it, VP9 is covered by patents, but the companies hope that they own all the relevant patents and hence are in a position to grant a royalty-free license. Microsoft announced in September 2015 that it was starting work on VP9 for Edge.

Along with VP9 video, Microsoft is adding the Opus audio codec and the WebM container format that combines video and audio. Opus is developed by Xiph and combines technology from Xiph's CELT codec, designed for wideband audio, and Microsoft/Skype's SILK algorithm, designed for narrowband voice. The resulting Opus codec is suitable for a wide range of applications, from speech encoded at just a few kilobits per second up to high bitrate audio.

One sticking point with VP9 is that it currently lacks widespread hardware decoding support, making it more power intensive than H.264 in particular and increasingly its successor, H.265. Accordingly, Microsoft will be making it optional in Edge. Systems that have hardware support will expose the codec to the Web; systems that do not will not offer it by default. This can be overridden by end-users.

WebM support is initially being restricted to sites using the Media Source Extensions (MSE) adaptive streaming specification. MSE extends the basic audio and video support to allow a stream's bitrate to be changed to accommodate changes in network conditions. Microsoft is also planning a limited implementation of the older VP8 codec, which will be used not for streaming media but for WebRTC video calling.

YouTube is perhaps the biggest driver for this change, with Google using WebM, VP9, and Opus extensively on its video site. With the volume of video that YouTube serves, the efficiency improvement that VP9 offers is particularly valuable, and the codec is already preferentially used in Chrome.