Free browser tool
Get an MKV out of VLC and into everything else
Drop an MKV in and get an MP4 back, usually in a second. It converts in this tab, on your own machine.
- No sign up
- Nothing uploaded
- No queue
- Up to 300 MB a file
Drop a MKV in
Drag a file onto this panel or open one. It is converted to MP4 in this tab, on your own machine, and never uploaded.
This is a remux, not a conversion
An MKV from OBS is almost always H.264 video and AAC audio, which is exactly what an MP4 holds. So the streams are copied from the Matroska container into an MP4 one, byte for byte. It takes about a second, nothing is re-encoded and nothing is lost. It is the same operation OBS's own "Remux Recordings" performs.
Where the MKV holds something an MP4 cannot carry, the page re-encodes to H.264 instead and takes considerably longer.
Why OBS records MKV at all
Because an MP4 is written with its index at the end. If the recording is interrupted, by a crash, a full disk or a power cut, that index is never written and the file is often unreadable. Matroska survives it. OBS's advice is to record to MKV and remux afterwards, which is the step most people skip until their editor refuses the file.
What gets dropped
The first video track and the first audio track are kept. Matroska can carry several audio languages and a stack of subtitle streams; an MP4 is not usually expected to, and they do not survive the remux.
It stays on your machine
ffmpeg runs in this tab, so a gameplay recording, a captured call or an internal demo is converted on your own processor and never uploaded.
Gameplay files are often far larger than this page's 300 MB ceiling, which is the tab's memory rather than a policy. Those are better remuxed in OBS itself.
How it works
Converting in 3 steps
- Drop the MKV inA recording from OBS, a download, an export that came out as Matroska. Up to 300 MB.
- ConvertWhen the video and audio are already H.264 and AAC, they are copied into an MP4 container untouched. Anything else is re-encoded.
- DownloadThe MP4 opens in every editor and plays on every phone, which is what the MKV would not do.
What it does
Free, and still worth using
Finish almost immediately
An MKV from OBS is usually H.264 and AAC already, which is exactly what an MP4 holds. The streams are copied into the new container rather than re-encoded, so it takes about a second and loses nothing.
Stop depending on VLC
Matroska plays in VLC and in very little else. MP4 plays in QuickTime, in Windows, on every phone, in every browser and in every editor.
Recover a recording that will not import
OBS writes MKV because an interrupted recording survives it. Rewrapping to MP4 is the step that was always meant to follow, and it is the same lossless copy OBS does itself.
Convert without an upload
Everything happens in this tab. A recording of a game, a call or an internal demo is never sent to a server.
On a Mac, the editing is already done
Prequel records your screen at its full resolution, then opens an editor with the zooms already placed, your camera framed and a background applied. Export one MP4 at up to 4K.
No credit card required
- Zooms placed on every click
- Camera shaped, sized and framed
- Background, padding and shadow
- Microphone and system on separate gains
- Cursor smoothed and resized
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A QuickTime recording in, its audio out as an MP3.
FAQ
Speed, tracks and compatibility
Why was that nearly instant?
Because an MKV usually needs rewrapping rather than converting. Matroska and MP4 can both hold H.264 and AAC, so the streams are copied into the new container untouched. It is a file copy, and it is lossless.
Does it lose quality?
Not when it rewraps, which is the common case. When the MKV holds something MP4 cannot carry, the video is re-encoded to H.264 at CRF 23 and the page takes longer.
What happens to subtitles and extra audio tracks?
They are dropped. Matroska can carry several audio tracks and subtitle streams; this conversion keeps the first video and the first audio track, which is what an MP4 is normally expected to hold.
Why does OBS record MKV instead of MP4?
Because an MP4 that loses power mid-recording is often unreadable, while an MKV survives it. OBS recommends recording to MKV and remuxing afterwards, which is exactly what this page does.
Is my recording uploaded?
No. ffmpeg runs in this tab, so the MKV is converted on your own processor and never sent anywhere.
What size can it handle?
About 300 MB. Game and gameplay recordings are often much larger, and those are better remuxed on your machine with ffmpeg or with OBS's own remux tool.
Will the MP4 play on a TV or a console?
Where the MKV did not, usually yes. H.264 in an MP4 is the most widely decoded combination there is.
Is there a recorder that writes MP4 to start with?
Prequel records your Mac's screen straight to MP4, at up to 4K and 120 fps, with the zooms already placed and the camera framed when the editor opens.