Firefox AV1 Decoding Rollout on Desktop

Mozilla played a foundational role in the adoption of AV1, rolling out decoding capabilities to the Firefox desktop browser through a phased approach that spanned several years. Beginning with initial experimental support, Mozilla transitioned from early reference software decoders to the high-performance dav1d library, enabling efficient software playback across Windows, macOS, and Linux before eventually introducing hardware-accelerated decoding on modern systems.

Early Implementation and AOMedia Roots

Mozilla was a founding member of the Alliance for Open Media (AOMedia), formed in 2015 to create a royalty-free, next-generation video codec to rival HEVC/H.265. Because of this foundational involvement, Mozilla prioritized native support for AV1 well before consumer hardware decoders existed.

Initial experimental support arrived in Firefox Nightly in early 2018 using the reference decoder, libaom. By October 2018, Firefox 63 introduced an optional preference (media.av1.enabled) that allowed users to test AV1 decoding manually. In January 2019, Firefox 65 officially enabled AV1 support by default for Windows desktop users, initially targeting 64-bit systems.

The Adoption of the dav1d Decoder

The reference libaom decoder was computationally demanding and frequently caused high CPU utilization and dropped frames on consumer hardware. To resolve this, VideoLAN, the VLC team, and the FFmpeg project developed dav1d, a highly optimized, open-source AV1 decoder sponsored by AOMedia.

Mozilla integrated dav1d into Firefox 66 as an option and enabled it by default across all desktop platforms—Windows, macOS, and Linux—in Firefox 67, released in May 2019. The integration of dav1d was a turning point for AV1 adoption, offering multi-threaded architecture and hand-crafted assembly optimizations for x86 and ARM processors. This drastically lowered playback overhead, allowing typical desktop processors to decode 1080p and even 4K AV1 video smoothly purely through software decoding.

Phased Hardware Acceleration

While dav1d made software decoding viable on mainstream CPUs, decoding high-bitrate 4K and 8K video without draining laptop batteries required dedicated hardware decoding blocks on graphics processing units (GPUs).

Mozilla rolled out hardware-accelerated AV1 decoding gradually as hardware and driver support matured:

By pairing early software optimization through dav1d with progressive hardware offloading, Mozilla ensured that Firefox users could stream AV1 content efficiently across varied desktop configurations.