MKV to MP4 Converter: Remux Matroska Videos in Seconds
Convert MKV (Matroska) videos to MP4 in your browser. H.264 MKV files from OBS and other recorders are remuxed in seconds with no quality loss. No upload.
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Your files never leave your device
About this tool
This MKV to MP4 converter moves Matroska videos into the MP4 container that phones, TVs, social apps and video editors expect. MKV is a flexible open container that can hold almost any codec, many audio tracks, subtitles and chapters. That flexibility is why OBS Studio records to MKV by default and why many players still refuse it. Most MKV files already contain H.264 video, so the conversion is usually a remux: a lossless copy that takes seconds. It all runs in your browser.
How to convert MKV to MP4
- Drop the MKV file on the page or click to choose it.
- Read the plan in the panel: fast copy, audio only conversion, or full re-encode.
- Click Convert to MP4. If a re-encode is needed, choose High quality or Balanced first.
- Preview the MP4 and download it.
What happens to each kind of MKV
| Inside the MKV | Result in MP4 | Time |
|---|---|---|
| H.264 + AAC (OBS default) | Remuxed, identical quality | Seconds |
| H.264 + AC-3, FLAC, Opus or Vorbis | Video copied, audio converted to AAC | Seconds to a minute |
| H.265 / HEVC, VP9 or AV1 | Re-encoded to H.264 + AAC | About real time or faster |
| DTS or TrueHD audio | Browsers cannot decode it: the video is saved without sound and you are told | Seconds |
Tips for MKV files
- OBS users: keep recording to MKV, which survives crashes, and remux here when you are done. In OBS, set the encoder to x264 or NVENC H.264 and AAC audio for an instant remux.
- Several audio tracks? The MP4 keeps the main video and the main audio track. Separate tracks for game, microphone or other languages are not carried over.
- Subtitles and chapters stay in the MKV. Keep the original if you need them.
- Need it smaller for upload or chat? Run the MP4 through the video compressor.
Private by design
The MKV is read and written on your device with the browser's WebCodecs engine; nothing is uploaded, and there is no file size limit beyond your device's memory. Only want the audio from a recording? Use the MP4 to MP3 converter, which reads MKV too.
Features
- Remuxes H.264 MKV to MP4 in seconds, with no quality loss
- Ideal for OBS Studio recordings saved as MKV
- Converts AC-3, FLAC, Opus or Vorbis audio to AAC when needed
- Re-encodes H.265, VP9 or AV1 MKV files to H.264
- Shows the codecs inside the MKV before converting
- Runs in your browser: the video is never uploaded
Frequently asked questions
How do I convert MKV to MP4?
Drop the MKV file on this page and click Convert to MP4. If the video is H.264, it is remuxed into an MP4 in seconds without re-encoding.
Does converting MKV to MP4 lose quality?
Not when the MKV holds H.264 video: the streams are copied and the picture is identical. Only H.265, VP9 or AV1 videos are re-encoded, and High quality keeps them close to the original.
How do I convert OBS MKV recordings to MP4?
Drop the OBS recording here and convert it. With OBS's usual H.264 and AAC settings, the MKV is remuxed to MP4 in seconds, just like the Remux Recordings option in OBS.
Are subtitles and extra audio tracks kept?
No. The MP4 contains the main video track and the main audio track. Subtitles, chapters and additional audio tracks remain only in the original MKV.
Is my MKV uploaded?
No. Everything happens in your browser. The file never leaves your computer, so large recordings convert without waiting for an upload.
Why is there no sound in my converted MP4?
The MKV audio is probably DTS or TrueHD, which browsers cannot decode. The tool tells you when this happens. Convert the audio with a desktop app, or re-record with AAC audio.