Free tool
Free MKV to MP4 converter for OBS recordings
Convert MKV to MP4 without uploading the file.
Your video
Drag a file here, paste it, or choose one.
.mkv, .mp4, .mov, .m4v, .webm, .avi, .wmv, .flv, .3gp, .gif. Up to 500 MB.
Up to 10 minutes long.
Your video never leaves your browser. The conversion runs on this machine.
More options
Result
Worked example
Measured on our own 20 second OBS style MKV, H.264 at 1080p60 with AAC, converted to MP4 with fast mode on.
Source MKV
6.9 MB
MP4, streams copied
7.0 MB
Done in under 5 seconds, including the engine download. Nothing was re-encoded, so all 60 frames a second and every pixel are as OBS wrote them. The size barely moves because only the wrapper changed.
1. Add the MKV. 2. Keep fast mode on. 3. Rewrap locally. 4. Download the MP4.
What Interlace does
Recorded a walkthrough in OBS? Make it from the SOP instead.
- Upload the procedure as it is
- One clear scene for each step, narrated
- When the procedure changes, edit the scene, not the recording
Real Interlace output, unedited. Shown silent and sped up.
Your file
2026-10-07 14-02-11.mkv
OBS screen recording
Questions
Asked and answered
No. The file is opened by the page and converted by ffmpeg compiled to WebAssembly, on your own machine. There is no upload step, and closing the tab discards everything.
An MP4 writes its index at the very end. If OBS or the computer crashes mid recording, that index never gets written and the whole file is unreadable. MKV writes as it goes, so a crash costs you only the last moments. Recording MKV and converting afterwards is the safe habit.
If OBS is open on the same machine, File, Remux Recordings does the same rewrap and is a fine choice. This page helps when the recording is on another computer, when you also want to trim it or shrink it to 720p, or when the MKV holds something MP4 cannot take as it is.
OBS can record game, microphone and chat to separate tracks. The MP4 gets the first audio track only, which in a default OBS setup is the full mix. If you need the tracks apart, use a desktop editor.
No. Only the video and the first audio track are written. Subtitle tracks, attachments and chapters are left out.
500 MB and 10 minutes. Everything runs inside one browser tab, which has a fixed memory budget, and the encoder runs on a single thread. A rewrap takes seconds; a full re-encode runs at about real time for 720p and several times the clip length for 1080p. For anything bigger, a desktop encoder such as HandBrake is the better tool.
Turn this into a video
Create an account and start from a document, script, or prompt.