Does my MKV get uploaded to a server?

No. Everything runs in your browser with WebCodecs. Your MKV never leaves your device. No upload, no watermark, no account.

Is the conversion lossless?

If your MKV already holds H.264 video and AAC audio, the streams are remuxed straight into the MP4 container. That part is near-instant and pixel-for-pixel lossless. Other codecs like HEVC, AV1, and VP9 are re-encoded to H.264, which is a normal lossy step.

It says my browser can't encode H.264. What now?

When the source has to be re-encoded, MP4 needs an H.264 encoder. Chrome and Edge have one. Firefox does not. Open this page in Chrome or Edge and try again.

MKV to MP4

Copies a matching H.264 stream when it can, or re-encodes to H.264 and AAC when it can't.

What this does

Convert MKV (Matroska) video to MP4. When your MKV already holds H.264 and AAC the streams are remuxed straight across; other codecs are re-encoded to H.264 and AAC. Everything runs in your browser with WebCodecs.

How it works

1Drop your MKV (Matroska) file or pick it from your device.
2Hit Convert to MP4 and watch the progress bar.
3Download the MP4. It plays on phones, TVs, and any editor.

Built with open source

Mediabunny — Converts and edits video and audio in the browser via WebCodecs. Add-on encoders cover MP3, AAC, and FLAC. · MPL-2.0

Frequently asked questions

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