Got an OBS recording or a download stuck in MKV? MKV to MP4 here is usually just a container swap: drop videos anywhere on this page and each one is rewrapped losslessly and near-instantly, because the H.264 video inside a typical MKV is exactly what MP4 wants. No upload, no size caps, no signup.
Why everything records MKV and nothing accepts it
OBS defaults to MKV for a good reason: if your PC crashes mid-recording,
an MKV survives and an MP4 doesn't. But Premiere, PowerPoint, iPhones and
most players want .mp4. Since OBS records H.264 (or you can
set it to), the fix is a pure container swap: same pixels, new envelope,
done in seconds. And that's the part converter sites hope you never learn.
A 20 GB gameplay recording would take an afternoon to upload somewhere,
wait in their queue, and download again, all for a job your own machine
finishes before you can alt-tab.
When you need Force H.264
Some downloaded MKVs carry codecs MP4 can't hold or your player can't decode (HEVC on an old PC, VP9, old XviD rips). If the instant rewrap produces a file that opens but shows a black screen or no image, run it again with Force H.264: a real re-encode, accelerated by your hardware encoder, into the codec everything on earth plays. The result note on each card tells you which path your file took.
FAQ
Is there a file size limit?
No hard cap. Multi-GB OBS recordings work best on a computer in Chrome.
Does the quality change?
Not in rewrap mode. The video and audio bits are copied untouched into the MP4 container, which is why it finishes in seconds. Force H.264 re-encodes, and even then it targets visually identical quality.
Is my video uploaded?
Never. Your recording is never uploaded, stored, or seen by anyone. The rewrap happens instantly and privately on your own hardware, which is also why a 10 GB file finishes here before it would clear 2% of an upload bar anywhere else.