Convert MKV to MP4
Rewrap MKV files as MP4s that phones, TVs, editors and social sites accept, all on your device.
- Nothing is uploaded
- Works offline after first visit
- Open source
- No watermark · limit is your device’s memory; phones hold less
Convert MKV to MP4 in your browser. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The size limit is your device’s memory, and phones hold less; give the page a short while after one visit to save itself for offline use, and then it works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
MKV (Matroska) is a flexible container: OBS records to it by default because an MKV survives a crash mid-recording, and many downloads use it. But iPhones, a lot of smart TVs, Premiere and most social sites want MP4. An MKV from OBS usually holds H.264 video and AAC sound, which fit in an MP4 unchanged.
This page copies those streams straight into an MP4 container, the same job as OBS’s own Remux Recordings, so a one-hour recording is ready in about the time it takes to read the file, with the picture untouched. MKVs with VP9, AV1 or other video are re-encoded by your browser. Only the main video and sound tracks are kept: extra audio tracks and subtitles are left out.
Everything happens in your browser. Game recordings, meetings and downloaded files stay on your machine, with no upload, limited by your device’s memory (phones hold less).
Newer OBS setups often record in HEVC or AV1 using an NVIDIA, AMD or Intel hardware encoder, and those recordings are not simply copied. AV1 is re-encoded to H.264, or to VP9 in a browser without an H.264 encoder. HEVC is re-encoded to H.264 when your browser can decode HEVC, and copied into the MP4 as HEVC when it cannot, which plays on Apple devices, Android and recent Windows. The line under each result says whether the video was copied or re-encoded, and to which codec.
Films and series downloaded as MKV often carry sound that MP4 players handle badly, such as FLAC, Opus, AC-3 or DTS. When your browser can decode that sound, it is converted to AAC in stereo, and surround tracks are mixed down to two channels. When it cannot, which on many systems includes AC-3 and DTS, the MP4 is written without sound and the result line says the sound was left out. AAC and MP3 sound, the usual case for OBS, is copied untouched.
How it works
- Drop one or more MKV files, or tap to pick them.
- Tick Remove the sound if you only need the picture.
- Convert, then open or upload the MP4.
In your browser, not on a server
Mediabunny (MPL-2.0), a media toolkit written in TypeScript, reads the MOV, MKV, WebM or MP4 container in your tab. H.264 video and AAC or MP3 sound are copied into the new MP4 packet by packet, which takes seconds and changes nothing in the picture. Other video (VP8, VP9, AV1) is decoded and re-encoded by your browser’s own video encoder through WebCodecs, H.264 where available, and other sound becomes AAC or Opus. The MP4 is written in memory.
Compared with upload-based tools: Online converters upload the whole video just to rewrap it, which can take longer than the conversion itself, cap free files at 100 MB to 1 GB, and keep a copy on their server. Here the file never leaves your device, and a large MOV from your phone converts in seconds because nothing is re-encoded that does not need to be.
Verify it yourself. Give the page a short while after one visit to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Are subtitles and extra audio tracks kept?
No. The MP4 gets the main video track and the main sound track. If you need a second language or burned-in subtitles, use a desktop tool such as HandBrake.
Is this the same as OBS Remux Recordings?
For an H.264 recording, yes: the streams are copied into MP4 without re-encoding. It is handy when you are on another computer, or when the recording was made with other software.
Will an MKV from a crashed recording convert?
Usually, yes. That is the reason OBS records to MKV: the file stays readable up to the moment the program or the computer stopped. The page reads what is there and writes an MP4 of that length. The last few seconds before the crash may be missing, since they had not yet been written to disk.
Can I convert a whole folder of MKV recordings?
Select them all at once and they are converted one after another; several download together as a zip. Each MP4 keeps the name of its MKV with the new extension, so an OBS file called 2026-09-29 20-15-03.mkv becomes 2026-09-29 20-15-03.mp4 and your recordings stay in date order.
Why does my MP4 have no sound?
The MKV's sound was in a format your browser cannot decode, most often AC-3 or DTS surround from a film download, so it could not be converted and was left out; the result line says so. Trying another browser may help, since Safari and Edge decode more formats on some systems. Otherwise convert the sound with a desktop tool such as HandBrake.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. Give the page a short while after one visit to save itself for offline use; then you can turn off Wi-Fi and it still works.
More video and audio tools
Video to MP4
Turn MOV, MKV and WebM files into MP4s that play everywhere. Converted on this device, never uploaded.
Audio converter
Turn any sound file into MP3, WAV, FLAC, M4A or OGG. Your files are converted on this device and never uploaded.
Screen recorder
Capture your screen, one window or a tab, with its sound and your voice. The video is made in this tab and never uploaded.
Voice recorder
A voice memo, a voice-over or a quick demo, recorded in this tab and saved as MP3. The sound never leaves your device.
Other conversions
Guides
- How to convert MOV to MP4MOV plays fine on Apple devices but not everywhere else. Here is how to convert it on a Mac and on Windows.