Mozilla Firefox Officially Gets MKV Video Playback Support

Update, October 2025:
Mozilla has confirmed that Firefox Nightly 145 now supports Matroska (MKV) video files using all the most popular codecs: AVC (H.264), HEVC (H.265), VP8, VP9, AV1 for video, and AAC, Opus, Vorbis for audio.
Just drag and drop any compatible MKV file into the browser’s address bar, no add-ons or conversions needed.

If you are on an older Nightly build (before version 145), you may still need to enable the media.mkv.enabled setting in about:config and restart the browser.

Original article continues below.

Great news for Firefox users: after making PWA support available for testing, the browser is finally gaining the ability to play MKV video files directly, a feature that Chrome and Edge have supported for years.

Until now, trying to open an MKV file in Firefox wouldn’t work. Instead, the file would either fail to load or trigger a download, forcing users to convert it, install an add-on, or switch browsers.

MKV (Matroska Video) is a video file format that can pack video, audio, and subtitles into a single file. It works with many modern video and audio types, which is why it’s popular among creators and video fans. Since Firefox couldn’t play MKV until now, this has been a major frustration for users.

Even Windows 10 and Windows 11 support MKV playback out of the box, making Firefox’s gap even more noticeable until now.

Firefox to Play MKV Videos Natively

Mozilla’s Plan

Mozilla has now assigned an engineer to implement MKV playback in Firefox. According to Mozilla’s technical brief, the rollout will happen in stages:

• Testing in Firefox Nightly with the most common setups first, such as H.264 video with AAC audio.
• Expanding codec support to cover formats like VP9 or AV1 paired with Opus or FLAC.
• Full release once stability and compatibility checks are complete.

Mozilla hasn’t given an exact release version yet, but the testing phase is already in motion. Once development and quality checks are finished, MKV support will be rolled out to all Firefox users.

This move finally brings Firefox in line with Chromium browsers, making video playback easier and removing a long-standing annoyance for many users.

That’s not all. Firefox has fixed a long-standing Virtual Desktop bug on Windows and added Google Lens support for image searches. Additionally, Firefox will not delete downloaded PDFs in private browsing and will be able to reinstall itself after a Windows 11 upgrade.