Prevention guide
OBS MKV vs MP4: the recording setting that prevents corrupted files
If OBS has ever crashed and left you with an MP4 that will not open, the safest fix is prevention: record to MKV, then remux to MP4 when the recording is finished. If your workflow needs MP4 directly, fragmented MP4 is the safer MP4 option.
Why standard MP4 is risky in OBS
A normal MP4 depends on metadata that is finalized when recording stops. If OBS crashes, Windows loses power, or the drive fills before that final write, the MP4 may be missing its index. The media data can still be on disk, but players do not know how to read it.
This is why broken OBS recordings often show errors like moov atom not found. The recording is not necessarily empty; it is unfinalized.
Why MKV is safer
MKV does not rely on the same final MP4 index step. If the recording is interrupted, the MKV is much more likely to remain playable up to the point of the crash. Afterward, OBS can remux that MKV to MP4 without re-encoding.
Best default: set OBS to record MKV, then use OBS's remux feature to create an MP4 for editing or uploading.
MKV vs MP4 vs fragmented MP4
| Recording format | Best use |
|---|---|
| MKV | Safest default for long streams and crash protection |
| Standard MP4 | Convenient, but risky if OBS or the PC crashes before finalizing |
| Fragmented MP4 | Safer MP4 option because metadata is written in smaller pieces |
| MKV remuxed to MP4 | Best balance: crash-safe recording, MP4 output afterward |
How to switch OBS to MKV and remux
- Open OBS settings.
- Go to Output, then Recording.
- Set Recording Format to MKV.
- After recording, use File → Remux Recordings.
- Select the MKV and let OBS create the MP4.
Remuxing is fast because OBS is only changing the container. It is not re-encoding the video, so quality is unchanged.
When fragmented MP4 makes sense
Fragmented MP4 is useful when your workflow strongly prefers direct MP4 output. It writes file metadata incrementally, reducing the risk that one final write determines whether the whole recording opens. It is still worth testing with your editor and upload workflow before relying on it for paid or important work.
Already have a broken MP4?
If OBS crashed before you changed settings, StreamSalvage can try to rebuild the unfinalized MP4 locally using a reference clip.
Download StreamSalvage for WindowsFrequently asked questions
Should OBS record to MKV or MP4?
For most creators, MKV is safer because it remains usable if OBS crashes before the recording is finalized. You can remux the MKV to MP4 afterward without re-encoding or quality loss.
Does remuxing MKV to MP4 reduce quality?
No. OBS remuxing changes the container from MKV to MP4 without re-encoding the video or audio streams, so quality stays the same.
Is fragmented MP4 safe in OBS?
Fragmented MP4 is safer than standard MP4 because metadata is written incrementally. It can be a good option when your editor or workflow needs MP4 files directly, but MKV plus remuxing is still the conservative default.
What should I do if I already recorded to MP4 and OBS crashed?
Make a copy of the broken file, avoid overwriting it, and try a local repair tool. A short reference clip recorded with the same OBS settings can help rebuild the missing MP4 metadata.