WebM is just Mastroska with most features disabled that are not relevant to streaming and a mandated set of codecs, so basic Mastroska support would have been possible years ago, simply by accepting the Matroska MIME types.

It’s highly popular in the anime scene for its ability to contain original audio and dubs and a few subtitle tracks, including custom fonts for some of the subtitle formats that are feeling particularly special.

Also not entirely sure what I would use it for since I’ve mostly seen it with rips of Blu-ray movies and shows, never smaller files. I thought its main advantage was holding multiple video, audio, and data streams.

WebM shows that Matroska is excellent for streaming. It’s the same container, WebM just mandates a set of codecs (just as MP4 as an offshoot of MOV can theoretically hold non-MPEG codecs but nobody supports this in the real world). With formal Matroska support, something like combining a HEVC video track with an Opus audio would be possible.

Being able to direct stream content from jellyfin without needing to repackage on the fly to another container would be nice.

It supports more complicated subtitles and menuing, more codec support (like a LOT more) lossless support, mode audio formats.

It’s like they took MP4 and added in all the stuff that you needed to replicate a BluRay, then added in lossless audio.

If you just want a movie with basic subtitles and audio, MP4 is fine. If you want to replicate newer stuff, MKV supports it.

The real hot part of this is if you have a collection of high-quality video/audio and you’re streaming it to firefox, you’ll natively be able to do so without transcoding.

It supports more codecs and I believe can store more tracks compared to MP4. Whenever I download a high quality movie or tv show, especially if it has multiple audio tracks and subtitles to choose from, it is always packaged in .mkv

More refined subtitle support (better timing, more flexibility in how they are presented and better timing) Complex chapter structure (think dvd menus and “bandersnatch” interactive movies and probably things nobody has thougth of doing because of lacks in the technology), segment linking (linking to a file and a timestamp, so you can reuse sections such as intros etc…) Arbitrary file support, to embed anything, text documents, subtitle font files, cover images, license information, client side storage High precision timestamps, rich metadata

One great thing is it can be extended, so it’s future proof, one bad thing is, it can be extended, so of course Apple made extensions that only work on their shit

Here is a pretty good write up on it. They aren’t that different but generally I think mkv is preferred in high quality since it can handle more tracks and more codecs.

After Firefox, by definition.

Because of MKV ?