Video conversion
Convert MKV to WebM
Updated Jul 2026
MKV is a flexible container that can hold near-original quality video along with multiple audio and subtitle tracks, but most web browsers won't play it directly. WebM is built for the web, so browsers and video-sharing pages open it natively. To convert, open the MKV in a converter and export it as WebM, ideally on your own computer so the video never has to travel anywhere first.
- Extension
- .mkv
- Type
- Video
- Typically
- High-quality video containers
- Extension
- .webm
- Type
- Video
- Typically
- Web video
- Compression
- Lossy
Convert MKV to WebM on your own computer. Nothing uploads.
How to convert MKV to WebM
- Open Morphjet and drag in the MKV file, or a whole folder of them, to convert several at once.
- Choose WebM as the output format.
- Convert. The WebM file is written next to your original, and nothing leaves your machine.
MKV vs WebM: what actually changes
| MKV | WebM | |
|---|---|---|
| File size | Larger, holds close to original quality | Smaller, compressed for web delivery |
| Quality | High, little to no loss | Good, but lossy on every export |
| Plays in web browsers | No, usually needs a download | Yes, plays inline without extra software |
| Multiple audio or subtitle tracks | Yes, can hold several at once | Typically just one of each |
| Works in common desktop media players | Yes, widely supported | Yes, though it's really made for browsers |
When to convert, and when not to
Convert MKV to WebM when you want to publish a video on a website, embed it in a page, or send it somewhere that expects a browser-friendly format instead of a download.
Keep the MKV original if you're archiving a high-quality copy or need to preserve multiple audio and subtitle tracks, since WebM usually keeps just one of each and compresses the video further.
Why not just use an online converter?
MKV files tend to be large, and an online converter needs you to upload the whole thing to its servers before it can hand back a WebM version, which takes a while and leaves your video sitting on a computer you don't control. Converting on your own machine skips the upload step entirely. The file goes in, the WebM comes out, and none of it crosses the internet.
Questions
Does converting MKV to WebM lose quality?
Yes, some. WebM is a lossy format, so each conversion re-compresses the video and drops some detail to hit a smaller file size. For web playback the difference is usually hard to notice, but it is a real, one-time loss.
Will the WebM keep all the audio and subtitle tracks from my MKV?
Often just one of each. MKV is built to hold several audio and subtitle tracks side by side, while WebM is generally set up around a single track, so extras may need to be handled separately or get dropped.
Why convert to WebM instead of just posting the MKV?
Most web browsers can't play MKV directly, so a page trying to embed it either fails or forces the visitor to download the file instead of watching it. WebM was built for browsers, so it plays inline without any extra software.
Can I convert MKV to WebM without uploading it anywhere?
Yes. A desktop app like Morphjet converts the file on your own computer, so the video never travels over the internet, even if the file is several gigabytes.
Morphjet converts MKV, WebM, and 1,800+ other formats, all on your machine. Launching this July.