MKV to MP4 Converter
Convert Matroska (MKV) files to MP4 for devices that do not support the container, with a clear account of what happens to extra streams.
Convert with this tool
or choose a file from your device — it is processed in this tab and never uploaded
Accepted: MKV (Matroska), including H.264, HEVC, VP9 and AV1 sources
Files stay on your device. There is no upload, no queue and no watermark, so a conversion works even with the network switched off after the page has loaded.
Supported formats & processing
| Accepted input | MKV (Matroska), including H.264, HEVC, VP9 and AV1 sources |
|---|---|
| Produced output | MP4 with H.264 video and AAC audio (primary streams) |
| Processing | FFmpeg.wasm (video engine, downloaded on first use) |
| Upload required | No — the file is read locally and never transmitted |
How to use this tool
- Add the .mkv fileThe container is read by the FFmpeg engine.
- Pick the qualityCRF 20–24 for a delivery copy, lower for an archival one.
- Set the audio bitrate192 kbps is a good default; 128 kbps is fine for dialogue.
- ConvertExpect a few minutes for a full-length film.
- Check what was carried acrossThe result card lists the output container and size.
About this tool
MKV is a flexible container that can hold any number of video, audio and subtitle streams — which is why it is the standard for rips, releases and archives. MP4 supports only one video stream and a limited set of codecs, so converting is partly a translation and partly a simplification.
This page maps the primary video and audio streams into an MP4 and re-encodes the video to H.264 so it plays anywhere. Subtitle streams cannot be carried into MP4 in a form that browsers can display, so the page tells you what it found rather than silently dropping it.
Features
- Reads Matroska directly with FFmpeg's demuxer
- Re-encodes to H.264 so phones and televisions play the result
- Primary audio stream converted to AAC at your chosen bitrate
- Quality controlled by CRF rather than a vague preset
- Honest reporting when extra streams cannot be carried into MP4
- Works with H.264, HEVC, VP9 and AV1 source video
Frequently asked questions
What happens to the extra audio tracks and subtitles?
MP4 can hold more than one audio track but browsers only expose the first, so the primary stream is converted and the rest are dropped. Subtitle streams cannot be carried into MP4 in a browser-displayable form. If you need them, keep the MKV and play it in a desktop player.
Why is the conversion slow?
Full-length films are large and the video must be re-encoded frame by frame. Expect roughly real time or a little faster on a modern laptop.
Can I convert without re-encoding?
Only if the MKV already contains H.264 video and AAC audio, and even then the container change has to be verified. Re-encoding is the reliable route.
Will subtitles be burned into the picture?
Not by default. Burning subtitles into the image is a separate operation, and it makes them impossible to switch off later.