What is this MKV to MP4 converter?
A free, browser-based tool that converts a MKV video to MP4. Add a file, preview it inline, and download the result. All processing happens locally in your browser, so your video is never uploaded and there is no watermark.
Finishing an OBS recording: MKV out, MP4 in hand
OBS writes MKV by default for a good reason: if the app or the PC dies mid-session, an MKV is still playable up to the last written second, while an interrupted MP4 is often a write-off. The catch comes afterward. Premiere Pro will not import MKV at all, phones and tablets handle it inconsistently, and plenty of upload forms only accept .mp4. So the standard routine for streamers and tutorial makers is: record to MKV for safety, convert to MP4 for everything downstream.
Why H.264 MKV to MP4 takes seconds, not minutes
OBS records H.264 on most setups (HEVC or AV1 on newer encoders), and MP4 can hold all three. That makes this conversion a remux: the compressed video is copied into the new container untouched, with zero quality change and no encoder involved. A 90-minute session finishes in roughly the time it takes to read and write the file. Since nothing is re-compressed, converting before you edit costs you no generation loss.
Multi-track audio: settle it before the MP4 step
One OBS habit deserves attention first: separate audio tracks. Many creators capture mic, desktop, and game audio as distinct tracks inside the MKV, which editing software reads happily. MP4 delivery normally assumes a single mixed track, and most players only play the first one they find. If you rely on per-track mixing, finish that work in your editor and export from there. Route the straight MKV to MP4 conversion at recordings with one mixed track: quick uploads, client shares, and files you simply want playable everywhere.
How to use it
- Add a MKV file on the left (drag & drop or click) — it shows an inline preview.
- Pick a quality preset (used only when the video has to be re-encoded).
- Press “Convert & download” to get your MP4 file. The first run downloads the ~30MB converter once.
Lossless remux vs re-encoding
MKV and MP4 are containers — what matters is the video codec inside. When the codec already fits MP4, this tool just repackages it (a "remux"): instant and completely lossless. Only when the codec isn't compatible — most often anything involving WebM — does it re-encode the video locally, which takes longer and is where the quality preset applies.