The file is there. The size looks right — a big file, clearly full of something. But the gallery shows a grey square instead of a thumbnail, the duration reads 0:00, and every player you throw it at says the same thing: this video is corrupt or unsupported.
Before you try anything, it helps to know what actually happened, because almost everything written about "fixing corrupt videos" skips it — and the fix only makes sense once you see the problem.
What actually broke (it's probably not your footage)
An MP4 or MOV file is written in two parts. The video and audio data stream into the file continuously while you record — frame after frame, straight to storage. Then, when recording stops normally, the camera writes a small table at the end: an index that tells any player where every frame starts, how long the video is, and how to decode it.
If the recording never stops normally — a flat battery, an app crash, a memory card pulled mid-write, storage that filled up — that index is never written. The footage is sitting in the file, usually intact. But without the table, a player cannot find the first frame, so it reports the whole file as corrupt.
This is why the broken file is often large and still useless. It is also why the fix is not "recovery" in the usual sense: nothing needs to be un-deleted. The index needs to be rebuilt around the data that is already there.
First, rule out the boring causes
Two minutes of checks before any repair tool:
- Did the file finish copying? A transfer interrupted halfway produces the same symptoms. If the original still exists on the camera, card, or in a chat app, copy it again and try that copy.
- Is it actually an MP4? A file renamed from another format will confuse players. The extension should match what recorded it.
- Try one other player. If the moov index is genuinely missing, no player will save you — but a file with minor damage sometimes plays in one app and not another. Worth one try, not an afternoon.
And one thing not to do: don't install "recover deleted videos" apps for this. Deleted-file recovery is a different problem. Your file is not deleted — it exists and won't open. Recovery scanners will churn through your storage and hand you back the same broken file.
The VLC trick everyone suggests — and its limit
Search this problem and you'll be told to open the file in VLC, which offers to repair it. That advice is half right: VLC has a built-in repair prompt, but it is for AVI files — a different, older container with a different index format. Point VLC at a truncated MP4 and there is no repair offer; it simply fails to play like everything else.
So for MP4 and MOV, the repair has to rebuild the index properly. There are three real ways to do that.
Option 1: fix it on your phone (where the video usually is)
Most broken recordings are born on a phone, a dashcam, a drone, or an action camera — and end up on a phone either way. Video Repair is our Android app built for exactly this failure: it scans the raw data in the damaged file, finds every frame boundary, and writes a fresh index around your original footage.
Three things about how it works are worth knowing before you tap anything:
- Checking, repairing, and previewing are free. You watch your own footage play inside the app before paying anything. If the recovery is poor, you've lost nothing. A single one-time purchase unlocks saving — no subscription. Current pricing is on the Video Repair page.
- Nothing is uploaded. The repair runs entirely on the device. For footage you'd rather not send to a stranger's server — family videos, work recordings — that is the whole argument.
- Nothing is re-encoded. The recovered video is your camera's own data copied through byte for byte, so there is no second round of compression and no quality loss.
It is honest about limits, too: most cameras repeat their picture settings inside the footage itself, so the video usually comes back from the damaged file alone. Sound is the exception — audio settings live only in the missing index, so recovering the audio track needs one healthy clip from the same camera as a reference. The app tells you which case you're in before you start.
Option 2: the open-source route (desktop, command line)
If you're comfortable with a terminal, untrunc is a well-known open-source tool that rebuilds truncated MP4/MOV files. It requires a reference video — a healthy file from the same camera with the same settings — and it runs on your computer, from the command line. No interface, no hand-holding, and results vary by camera, but it's free software doing the same fundamental job: reconstructing the index.
Option 3: desktop repair software
Commercial desktop tools — Stellar Repair for Video being the biggest name — handle a wider spread of formats and batch jobs on Windows and Mac. If your footage lives on a computer and you repair videos regularly, that category is worth a look; we compare it honestly in Stellar Repair for Video alternative, including where the desktop tools win.
What no tool can fix
Being straight about this saves you money and false hope:
- Overwritten data is gone. If the camera reused that part of storage, or the file was zeroed rather than merely left unindexed, there is nothing to rebuild. A good repair tool tells you this instead of producing a file that opens and plays garbage.
- Deleted files are a different problem. Repair tools fix files that exist. If the video was deleted, you need recovery, not repair — and the honest advice there is to stop writing to that storage immediately.
Whatever you try: work on a copy. The damaged file is your only source. Any tool worth using reads it without modifying it — Video Repair never writes to the original — but keeping a spare copy costs nothing and protects you from tools that are less careful.