Add support for Matroska Media Container (.mkv files)

[Steeltent]

The Bugzilla entry is five years old. Chrome can do this. It's annoying that Firefox can not.

Not being able to play .mkv files makes it impractical for some people to use Firefox. They need this feature to play videos from Plex or Jellyfin and to monitor their security cameras. These are just two examples of very common use cases. And in such cases users are forced to use a Chromium-based browser. They simply have no other choice.

That's why I think Firefox should add this feature as soon as possible.  

[zramdeen]

+1. it's reasons like this that prevent users from completely switching to firefox.

[cnr]

+1

[joda]

+1

[rockfarkas]

still waiting

[Userfoxxx]

Ждем

We are waiting

[Alessio89]

bump this. firefox now can use system hevc codec, mkv has no patent issues, so there are no more reasons to not support embedded mkv videos

[Alessio89]

I bump this. there is no more reason to not support embedded mkv since now firefox can use system HEVC codec.

[Erebus]

This is still not supported? Wow.

The most popular container format, a format with no patent issues, used in so many user cases, media servers for example?

We are in 2025 and matroska is not some kind of "exotic" media container today and is supported everywhere, Chrome, Edge etc.

https://www.ietf.org/rfc/rfc9559.html

[Grzesiek11]

While I am personally not affected by this, and I've never seen Matroska video on the web myself, I do support this.

It seems like there are some websites that make use of it, and many web developers do not check browser compatibility, so if it works in Chrome, they go with it. While this isn't great, it has the result of end users seeing a website that works in Chrome and does not in Firefox.

The argument of local content servers also does make sense. While I personally don't use my Nextcloud instance for video playback, if I did, it would not work without either me or Nextcloud itself remuxing to MP4 or WebM - some users also correctly pointed out that some decently common codec combinations would not be possible to remux and would require reencoding.

I also reported this to be tracked on caniuse.com: https://github.com/Fyrd/caniuse/issues/7347.

@teledyn wrote:

I just spent a morning trying to figure out why my Nextcloud MKV files all returned errors on Firefox but not on Chrome. How is it even possible?

It's possible by there being no code to support it. Format support requires code for handling the format to be present. It doesn't just magically appear.

FF is intentionally blocking?

No. I have no idea how do you even get to that conclusion.

[probablywrong]

No movement on this idea still, huh? Wild. It's one of the few things where you simply cannot ditch a Chromium browser because for whatever reason they're still the only ones to support .mkv, which is one of the most popular video formats.

[Yacine]

+1

[Vandon]

Why is this such an old incomplete feature request? The competing browsers have been able to play mkv for a long time now.

[lucaso]

+1

[wasp38b]

+1

[Grander]

HOW is this still not supported? I thought I was having some weird networking issues with Nextcloud, but no, it turns out the browser I've used for over a decade doesn't support a video format I was already watching (locally) a decade ago... Only problem I have ever had with Firefox, and it's such a stupidly basic one.