You recorded for forty minutes, the app crashed or the battery died, and now the file will not play — or there is no file at all. Whether anything can be saved depends on how the app was writing the video.
Why a crash can ruin a whole video
A video file is more than its frames. It also carries an index that tells a player where every frame and every second of audio sits. Many recording setups write that index only when you press stop. If the app never reaches that step — a crash, a phone that shuts down, an app ended without warning — the frames can be on disk with nothing to find them. To a player, the file is broken.
How recording apps avoid it
- Fragmented files. The app writes the index in pieces every few seconds. If recording ends abruptly, the file still plays up to the last piece.
- Closing the file on the way out. When you swipe away from an app, iOS gives it a moment to finish up. A careful app uses that moment to close the file properly.
Neither can be added afterwards. It depends on what the app did while it was recording.
What to try with a file that will not play
- Look in Photos first. If the recording app saves to Photos, check Recents and Recently Deleted.
- Try another player. Copy the file to a computer and open it in VLC, which copes with damaged files better than most players.
- Try a repair tool. Desktop tools can rebuild a missing index; the open-source untrunc is one. They usually need a working clip recorded on the same phone, with the same settings, as a reference. Results vary.
- Copy the damaged file off the phone before you record anything else in that app.
Avoiding it next time
- Choose a recording app that writes video in fragments. App Store listings rarely say so; the developer’s support page may.
- Keep the phone charged and cool. Those are the two most common reasons a long recording ends abruptly. Why does my iPhone stop recording video? goes through the rest.
- Split important sessions. Stopping and starting a new recording now and then means one failure never costs you everything.
How NoLight writes video
NoLight writes every recording in five-second fragments. To test it, I ended the app mid-recording in a way that gave it no chance to close the file. The recording played back complete, with picture and sound, right up to the moment it was ended. When you leave the app normally, NoLight closes the file straight away. How to record a long video on iPhone without losing the file has the longer story.
Short answers
Can a corrupted iPhone video be fixed? Sometimes, with a desktop repair tool and a reference clip from the same phone. Not always.
Why won’t my video play after the app crashed? It is probably missing the index a player needs, which many apps only write when recording stops.
How do I stop it happening again? Use an app that writes video in fragments, and keep the phone charged and cool.