VP9 is a royalty free video compression format (also known as a video codec).
VP9 was open sourced by Google and is seen by Google as the successor of VP8.
VP9 takes considerably more processing power than VP8, but produces better quality on the same bitrate (or lower bitrate for the same quality).
The VP9 decoder is already part of Chrome and used to decode YouTube videos whenever possible.
Google are planning to introduce VP9 into their WebRTC implementation in Chrome later this year.
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