Free tool
MKV to MP4 converter
This MKV to MP4 converter moves the video and sound of an MKV into an MP4 without re-encoding them, which is what an OBS recording or a downloaded film needs. A 30-second 1080p OBS-style recording took a fraction of a second.
- Free
- Remuxed, not re-encoded
- Nothing is uploaded
Drop your MKV video here, or Choose your MKV video
MP4, MOV, WebM or MKV, up to 2 GB and 3 hours. Everything happens in your browser; nothing is uploaded.
How it works
How do you convert MKV to MP4?
Add the MKV. The converter reads its tracks, keeps the main video and sound, and writes them into an MP4 as they are, so even a long recording takes seconds. If the video is VP9 or AV1, which MP4 players rarely expect, it is re-encoded as H.264.
- 1
Add the MKV
An OBS recording from your Videos folder, or any other MKV.
- 2
Convert to MP4
The page says what it will copy; for an OBS file that’s everything, so it finishes almost at once.
- 3
Use the MP4
Open it in an editor, send it, or upload it where MKV isn’t accepted.
Why does OBS record in MKV?
Because an MKV that stops suddenly, after a crash or a power cut, still plays up to that point, while an unfinished MP4 can’t be opened at all. MKV is the safe way to record and MP4 the easy way to share, so recordings get remuxed afterwards.
OBS can remux its own recordings: File → Remux Recordings. This page does the same job in the browser, on any computer, without OBS installed.
Does converting MKV to MP4 lose any quality?
Not when it’s a remux, which it is for H.264 and HEVC video. The frames are copied into the MP4 byte for byte; only the container around them changes. Our 22 MB 1080p recording came out as a 22 MB MP4 that decodes without errors.
- H.264 or HEVC video
- In the MP4Copied as it is
- VP9 or AV1 video
- In the MP4Re-encoded as H.264
- AAC or MP3 sound
- In the MP4Copied as it is
- AC-3 or E-AC-3 sound
- In the MP4Copied as it is (MP4 can hold it)
- Opus sound
- In the MP4Re-encoded as AAC
- FLAC sound
- In the MP4Re-encoded as AAC in Chrome and Edge
- Subtitle tracks, extra audio
- In the MP4Left out
| In the MKV | In the MP4 |
|---|---|
| H.264 or HEVC video | Copied as it is |
| VP9 or AV1 video | Re-encoded as H.264 |
| AAC or MP3 sound | Copied as it is |
| AC-3 or E-AC-3 sound | Copied as it is (MP4 can hold it) |
| Opus sound | Re-encoded as AAC |
| FLAC sound | Re-encoded as AAC in Chrome and Edge |
| Subtitle tracks, extra audio | Left out |
What happens to subtitles and extra audio tracks?
They’re left out: the MP4 gets the main video and the main sound track. A film with three languages and five subtitle tracks comes out with its default language and no subtitles. To put subtitles back, add them to the MP4 next.
Is there a simpler way to keep recorded calls?
Yes, if the point is what was said. NoteOwl records calls on your Mac from any app, without a bot, and gives you the transcript with each speaker, a summary and the action items, kept on the Mac and searchable.
FAQ
Questions about converting MKV to MP4
Is my MKV uploaded?
No. The MKV is read from your device and the MP4 is written in the page. In our tests the browser sent no network requests between choosing the file and saving the result.
Why does a long MKV convert so fast?
Because nothing is decoded. Remuxing reads each packet of video and sound and writes it into the new file, so the time depends on how fast the file can be read, not on how long the video plays.
Will the MP4 play on an iPhone?
An MP4 with H.264 or HEVC video and AAC sound plays on an iPhone. If the sound is AC-3 or E-AC-3, from a film, Apple devices play it too, but some other players and browsers don’t.
Can it keep the MKV’s subtitles?
No, subtitle tracks are left out. If you have the subtitles as an SRT file, the add subtitles to video tool can burn them into the MP4 or add them back as a track.
What if my MKV has VP9 or AV1 video?
Then the video is re-encoded as H.264, since most MP4 players don’t expect those codecs. That takes longer, in proportion to the video’s length; the page says so before you start.
Is there a size limit?
Files up to 2 GB and 3 hours long. Remuxing is quick at any length; a 2 GB recording mostly takes as long as your computer needs to read it.
Keep exploring
More video tools
- MP4 to WebM converterConvert an MP4 to a VP9 and Opus WebM in your browser, for a web page’s video or anywhere WebM is asked for
- Video compressorMake a video smaller in your browser: pick a size to fit (10, 25 or 100 MB, or your own) or a quality, and see the size before and after
- Video trimmerTrim the start and end off a video in your browser with handles over its frames; copied without re-encoding, or cut on the exact frame
- Remove audio from videoTake the sound out of an MP4, MOV, WebM or MKV in your browser; the picture is copied as it is, so it keeps its quality
Related
- Extract audio from videoTake the sound out of an MP4, MOV, WebM or MKV video in your browser and save it as MP3, M4A (no re-encoding) or WAV; nothing is uploaded
- Video to textTurn video to text free: drop in an MP4, MOV, M4V, MKV or WebM video and get an AI transcript with times, as text, SRT, VTT or Word; only the sound is sent, nothing is stored
- AI meeting notes without a botHow NoteOwl records calls from your Mac with no bot joining, and what you get when the call ends
Your calls, recorded and written up on your Mac
Free to download. Runs entirely on your Mac.
macOS 26 or later · Apple Silicon (M1 or newer) · 16 GB memory minimum, 24 GB recommended
About NoteOwl
NoteOwl is private AI meeting notes and memory for the Mac. It captures meetings without a bot joining the call, labels every speaker, writes summaries and action items, and builds a memory of every conversation that you can chat with — fully offline, because the speech recognition and the AI run on the Mac itself. Dictation into any app is free; Pro is a one-time purchase.
NoteOwl pricing: what’s free and what Pro adds
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