AOMedia Video 1 (AV1) is an open, free video encoding format originally developed for video transmission over the Internet. It was developed as the successor to VP9 by the Alliance for Open Media (AOMedia), a consortium founded in 2015 that includes semiconductor firms, video-on-demand providers, video content producers, software companies, and web browser vendors. The AV1 bitstream specification includes a reference video codec. In 2018, Facebook conducted near real-world testing and the AV1 reference encoder achieved 34%, 46.2%, and 50.3% higher compression rates than libvpx-vp9, x264 high profile, and main profile x264 respectively.
Similar to VP9, but unlike H.264 / AVC and HEVC, AV1 has a royalty-free licensing model that does not preclude deployment in open source projects.
Streaming Media Magazine's latest codec comparison from September 2020, which used moderate encoding rates, VMAF, and a diverse set of short clips, found that the open-source libaom and SVT-AV1 encoders took about twice as long to encode than x265 preset is "very slow" when using 15-20% lower bitrate, or about 45% lower bitrate than the very slow x264. The best AV1 encoder tested, Visionular Aurora1, in its "slower" preset, was very slow at x265 while maintaining 50% bitrate compared to x264 being very slow.