OBS recording corrupted after a crash? How to recover the MP4

By the FixMP4 engineering team · October 9, 2026 · 10 min read

You recorded a two-hour stream, a tutorial, or a game session with OBS Studio, and then something went wrong: OBS froze, the game took the whole PC down, Windows decided to update, or the power went out. When you open the recording you get "this file is not playable", "moov atom not found", or a file that shows 0:00. The recording is several gigabytes, so the data is clearly there. Why will it not play?

This guide explains what went wrong, how to get the recording back, and, most importantly, how to change one OBS setting so it never happens again.

Why OBS MP4 files break on a crash

When OBS records to MP4 or MOV, it writes the compressed video and audio frames into the file as they come out of the encoder. The file's index, called the moov atom, lists every frame's position, size and timing. OBS can only write it when it knows the recording is complete, so it writes it at the moment you click Stop Recording. (More on this in what is the moov atom.)

If OBS never gets to that moment, there is no index:

• OBS crashes or is killed from Task Manager.
• The PC blue-screens or freezes, often caused by the game or a driver.
• Power loss or someone flips the switch.
• Windows Update restarts the machine.
• The disk fills up mid-recording.

This is why OBS shows a warning when you choose MP4, and why its default recording format has long been MKV, which is designed to survive crashes.

Step 1: Check whether you actually recorded MKV

Look at the file extension in your recording folder (Settings, Output, Recording Path). If the file is an .mkv, it is probably not corrupted at all: MKV recordings remain playable up to the moment of the crash. Open it in VLC to check. To get an MP4, use File, Remux Recordings in OBS.

If the recording is fragmented MP4 or hybrid MP4 (options in recent OBS versions), it was also written to survive crashes. Try VLC first. If it plays, remux it to a regular MP4 if your editor needs one.

If the file is a regular .mp4 or .mov and will not open anywhere, continue below.

Step 2: Do not keep re-recording to the same folder

OBS names files by date and time, so it will not overwrite the broken file, but if the disk is nearly full, free some space before doing anything else. Copy the broken recording somewhere safe.

Step 3: Make a reference recording

Because the encoder settings (for H.264, the SPS and PPS parameter sets) were going to be written into the index, a short healthy recording made with the same OBS settings supplies them. To make one:

1. Do not change anything in Settings, Output or Settings, Video.
2. Click Start Recording, wait ten seconds, click Stop Recording.
3. Check that the new file plays.

The reference must match the broken recording's:

• Encoder (x264, NVENC H.264, NVENC HEVC, QuickSync, AMF).
• Base and output resolution and frame rate.
• Rate control and profile if you changed them.
• Audio tracks: same number of tracks and the same sample rate.

If you have since changed settings, change them back first. Our guide to choosing a reference file has more tips.

Step 4: Rebuild the index

Open the FixMP4 repair tool, drop in the broken recording and the reference, and let it scan. It works out where every video and audio frame starts and ends, rebuilds the index, and gives you a free preview so you can check the result. Everything runs locally in your browser, so even a 20 GB recording is never uploaded. If the preview looks right, export the full file with a subscription.

What you will get back

• All video up to roughly the moment of the crash. The last fraction of a second may be missing if the operating system had not written it to disk yet.
• The audio track, if it was AAC.
• If you recorded several audio tracks (for example game, microphone and Discord on separate tracks), be aware that only the main audio track is guaranteed to be rebuilt; check the preview.

What is not supported

Reading the preview

When the preview plays smoothly with correct colours and the audio in sync, the rebuild worked and the full export will match it. If the picture is full of grey or green blocks, the reference was recorded with different settings: the most common mismatch is a different encoder (for example the recording used NVENC but the reference used x264 because the GPU encoder was unavailable at that moment) or a different output resolution because a rescale filter was active. If the audio drifts out of sync over a long recording, check that the reference used the same audio sample rate, 44.1 kHz or 48 kHz, as set in Settings, Audio. Fix the setting, make a new ten-second reference and run the preview again. Previews are free, so trial and error costs only a few minutes.

Why not just use a recovery command?

You may find forum advice suggesting command-line tools such as Untrunc. These work on the same principle and can be useful, but they require building or installing software and running commands, and results vary with the encoder. FixMP4 does the same kind of index rebuild in a browser with a preview, so you can see whether it worked before investing more time. Our comparison of video repair tools covers the options honestly.

Prevent it: the OBS settings that matter

The most effective fix is to make crashes harmless:

1. Record to MKV (Settings, Output, Recording, Recording Format). Turn on Automatically remux to MP4 in Settings, Advanced, so you still get an MP4 when the recording ends cleanly.
2. Alternatively, choose fragmented MP4 or hybrid MP4 if your version of OBS offers them and your editor accepts the result.
3. Keep plenty of free disk space, and record to a fast drive that is not also used by the game.
4. Pause Windows Update before long recording sessions, and set active hours.
5. Update your GPU drivers: NVENC or AMF crashes are a common cause of OBS freezes.
6. For important streams, enable a local recording as backup and keep the stream VOD from your platform.

Recording to a USB drive or network share

Recordings written to an external drive or network share are more vulnerable: if the drive disconnects, the file is cut off in the same way as a crash. Record to an internal disk and copy afterwards.

Summary

A crashed OBS MP4 recording has all its frames but no index. If it is actually an MKV or a fragmented MP4, it probably plays already. If it is a regular MP4 with H.264 or HEVC, record a ten-second reference with the same settings and try a free repair preview. Then switch to MKV or a crash-safe MP4 mode so it never happens again. For more about the MP4 format, see our MP4 repair guide.

• OBS
• screen recording