MKV to WEBM converter
Convert MKV to WEBM in seconds, free and unlimited. No upload, no sign-up, no watermark: your video never leaves your device.
Last updated
Quick answer: To convert MKV to WEBM, add the MKV file to the iHateFiles MKV to WEBM converter and press Convert. The conversion runs in your browser, so the file is never uploaded, and it is free with no sign-up, watermark or size limit. An open, royalty-free format that browsers play natively.
Should you convert MKV to WEBM?
Do this when something specifically needs WEBM. The picture is re-encoded, so it costs a little quality; if all you need is a file that plays everywhere, MP4 is usually the better target.
The picture is re-encoded
An MKV usually holds almost any codec, often H.264 or H.265 with several audio and subtitle tracks. This writes VP8 video with Vorbis sound into the WEBM. Both sides are compressed with loss, so this is a second generation: leave the quality at its default or higher, because the encoder is working from MKV artefacts rather than the original.
Extra tracks may not survive
An MKV can carry several audio tracks and subtitle tracks. WEBM is more limited, so this conversion keeps the main video and the first audio track. If you need the subtitles, save them first with Extract Subtitles.
Where the WEBM will play
WEBM plays on every modern browser and Android, but not QuickTime or older iPhones.
MKV and WEBM side by side
| MKV | WEBM | |
|---|---|---|
| Inside the file | almost any codec, often H.264 or H.265 with several audio and subtitle tracks | VP8 video with Vorbis sound |
| Compression | Lossy | Lossy |
| Carries sound | Yes | Yes |
| Plays on | VLC, Plex, most smart TVs and Android, but not the iPhone Photos app or QuickTime | every modern browser and Android, but not QuickTime or older iPhones |
| Here | Read and write | Read and write |
What usually goes wrong
About the MKV. MKV and WEBM share a signature because WEBM is a restricted Matroska, so tools sometimes report one as the other. What matters is the codecs inside.
About the WEBM. A browser screen recording is usually a WEBM with a broken duration, so players show it as zero seconds or refuse to seek. Converting it to MP4 rewrites the header and fixes the seeking.
How to convert MKV to WEBM
- Add your MKV file. It is read from your disk and stays there.
- Check the settings. The output format is already set to WEBM.
- Press convert and the WEBM file is saved back to your device.
Questions
How do I convert MKV to WEBM?
Open this page, add your MKV file, and press convert. The file is decoded and re-encoded by your own browser and saved back to your device. Nothing is uploaded.
Is this MKV to WEBM converter free?
Yes, completely. There is no account, no sign-in, no watermark and no daily limit, because there is no server doing the work. Your own device does it.
Are my files uploaded anywhere?
No. There is no upload endpoint. The conversion runs inside this browser tab, so your file never leaves your device. You can open your browser's network panel and watch: nothing carrying your file is sent.
Is there a file size limit?
No fixed limit. Because the work happens on your machine there is no server quota. The only ceiling is your own device's memory, which for video means very large files may be slow.
Will converting to WEBM lose quality?
WEBM is a lossy format, so some detail is discarded. The quality control on this page decides how much. The default is set high enough that most people cannot see the difference.
Can I convert several MKV files at once?
Yes. Add as many as you like and they are converted one after another, then offered as a single ZIP.