Firefox Finally Adds MKV Video Support After an 8-Year Wait

Firefox has finally moved to support MKV video files in its Nightly builds, following more than eight years of requests. According to the article, initial playback within MKV containers is limited to AVC/H.264 and AAC due to codec constraints, with support for additional codecs expected to roll out gradually. Users of Firefox Nightly can enable the feature by toggling the media.mkv[.]enabled setting and restarting the browser.

The development team has asked users to report any playback issues with MKV files containing AVC or AAC so problems can be analysed and resolved. The Matroska team, which oversees the MKV container format, welcomed Firefox’s adoption and outlined plans to reach the same maturity and reliability as Chrome and Chromium. The piece carries a September 12, 2025 date and notes MKV support is already present in other browsers, highlighting Firefox’s delayed but forthcoming addition.