How to use the mkv to mp4 converter
- 1
Select your file
Drag a file onto the box or click to browse. It stays on your device, nothing is uploaded.
- 2
Click Convert to MP4
FFmpeg runs in your browser. The first run also downloads the FFmpeg core, so it takes a little longer.
- 3
Download the MP4
When it finishes, download the MP4 file. Re-run with another file any time.
Remux instead of re-encode when compatible
MKV is a flexible container that often holds H.264 or H.265 video with AAC audio, all of which MP4 supports. In those cases the converter stream-copies the tracks into MP4 (-c copy) without re-encoding, keeping full quality and finishing quickly. Files with codecs MP4 cannot carry are re-encoded automatically.
Subtitles and multiple tracks
MKV frequently bundles several audio tracks and subtitle streams. A fast remux keeps the primary video and audio; complex multi-track or embedded-subtitle layouts may simplify during conversion, since MP4 handles tracks differently. For most single-audio movies and recordings, the result plays everywhere.
Frequently asked questions
Is the MKV to MP4 converter free?
Yes, it is free with no ads or sign-up, and it works entirely in your browser.
Does it upload my MKV file?
No. The file is processed locally with FFmpeg WebAssembly and never uploaded to a server.
Why convert MKV to MP4?
MP4 is supported almost everywhere, while MKV is not playable on many phones, browsers, and editors. Converting makes the file universally compatible.
Will I lose quality converting MKV to MP4?
No, when the codecs are compatible the tracks are remuxed without re-encoding, preserving quality. Only incompatible codecs trigger a re-encode.