Omni Converter

Convert

MP4 to MKV

Transcode to a Matroska MKV, the permissive open container, preferring AVC/AAC for player compatibility with trim, geometry, frame-rate, quality, tag, and naming controls.

Runs in your browser. Nothing is uploaded, nothing is stored, and the MKV output is validated before you see it.

Open the converterFree. No account. Drop several files at once if you like.

How it works

  1. Drop, pick or paste your MP4 file. It is recognised the moment it lands.
  2. Choose Video to MKV. Only conversions this file can really do are offered.
  3. Save. One file, a bundle, or a whole folder. On iPhone the share sheet opens so it lands in Files or Photos.

What you get

  • Matroska
  • AVC video
  • AAC audio
  • Open container

Engine: Mediabunny Conversion + WebCodecs AVC/AAC. Accepted inputs: MP4, WEBM, MOV, M4V, MKV.

Questions

Is my MP4 file uploaded?
No. The conversion runs inside your browser with WebAssembly and native browser decoders. The file never leaves your device; you can watch the Network tab stay empty while it converts.
Is there a file size or daily limit?
No limit set by us. The only ceiling is your device's memory, because everything happens locally. There is no queue, no account requirement and no daily count.
How do I know the MKV output is valid?
Every output is checked before it is offered: the bytes are re-read and the format signature, size and structure are verified. If a result cannot be validated it is not shown as a result.
Does it work on iPhone and iPad?
Yes. The same app runs in Safari and as the Omni Converter app on iOS, where Save opens the share sheet so the file lands in Files, Photos or any app you choose.

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