To fix an OBS recording free: drop the MKV anywhere on this page. It remuxes to MP4 on your device, losslessly copying the video and audio streams into a container Premiere imports, and saves back. No re-encode, no upload, and multi-GB recordings work.
Why OBS uses MKV (and why that's right)
If OBS crashes mid-stream, an MP4 recording would be a corrupt brick. An MKV survives to the last written frame. So keep recording to MKV; just remux before editing. OBS has a built-in remuxer, but it fails on certain audio settings and you may be on a different machine than your recording. This page works anywhere with a browser.
Fix the root cause too
In OBS, go to Settings, Advanced, Recording and check "Automatically remux to mp4". And if your remuxed files import with no audio: in Settings, under Output, set the Audio Encoder to AAC (PCM audio in MP4 confuses editors: the classic silent-import bug).
FAQ
Is quality affected?
No. Remuxing copies the video and audio streams bit-for-bit into a new container. Zero re-encoding.
My recording only imports as audio in Premiere.
That's the MKV problem this page fixes: Premiere reads the container partially. After the rewrap it imports normally.
10 GB recording, really no upload?
Really. That's the whole point: remuxing locally takes about as long as copying the file, versus hours of uploading.