Why does my file say it is corrupted, and can I repair it?
Either the file is genuinely damaged, or the program cannot read it for another reason. How to tell which, what can honestly be repaired, and where the real copy usually is.
- Difficulty
- intermediate
- Time
- 40 min
- Read
- 4 min
- Safety
- warning
Short answer
Work out first whether the file is damaged or simply misidentified — a wrong extension, an incomplete download or the wrong program produces the same message. Then try the application's own repair option, which exists in most office suites, and its autosave or version history. Copies are the realistic answer: a cloud version history, a backup, an emailed copy, or a temporary file the program left behind. Genuine repair of a badly damaged file rarely returns it intact.
Safety
Step by step
- Rule out the simple explanations first.An incomplete download or a copy interrupted partway. A wrong extension, so the correct program refuses it. Opening it in a program that does not support that version of the format. All produce corruption messages and none involve damage.
- Check the file size.A file of zero bytes contains nothing and there is nothing to repair. A file much smaller than expected was truncated during copying or downloading. Both point at re-obtaining rather than repairing.
- Try the application's own repair.Office suites include an open-and-repair option, usually in the open dialogue, which recovers a surprising amount from a damaged document or spreadsheet. It is the first genuine repair route and costs nothing.
- Look for the program's own copies.Autosave files, temporary files, and version history within the application. A word processor or spreadsheet frequently still holds a version from minutes before the file broke, in a location that survives the damage.
- Look for copies outside the file itself.Cloud version history, your backup, an emailed copy, a copy on another machine, a copy on a USB stick. This is where these situations are actually resolved, far more often than by repair.
- Check the drive if more than one file is affected.One corrupt file is bad luck. Several is a symptom. Read the drive's health data and run the file system check — and back up before you do either.
- Understand what repair tools can and cannot do.For structured formats — documents, spreadsheets, archives, some video — a repair tool can rebuild the structure around intact data and often recovers most of the content. Where the damage is in the data itself, nothing recreates what is missing. Photographs and video may come back partially: an image with half the frame, or video that plays to the point of damage.
- Be wary of paid repair software.Same posture as recovery software. Use tools that show you a preview of what they can recover before payment, and do not expect a badly damaged file to come back whole.
- Work on a copy, always.Copy the damaged file before running anything against it. Repair tools rewrite files, and a failed repair on your only copy removes the chance of trying another approach.
If it doesn't work
Document will not open in the program that made it
Cause: Structural damage, or an interrupted save — Fix: Use open-and-repair, then look for autosave copies. If the file was on a network or removable drive when it was saved, that is very likely the cause.
Photographs show as grey or half-rendered
Cause: Partial data loss, commonly from a card pulled mid-write or a failing card — Fix: The visible part is what survived. Recover from the card with photo recovery software before overwriting it, and treat the card as suspect afterwards.
Archive reports it is damaged or incomplete
Cause: Incomplete download, or a multi-part archive missing a part — Fix: Re-download. Archive tools have a repair function that works if the archive was created with recovery information, and not otherwise.
Video plays partway then stops
Cause: Recording interrupted — a flat battery, a full card, or a crash — leaving the index unwritten — Fix: Tools exist that rebuild a video index using a good file from the same camera as a reference, and they work well for exactly this case.
Files became corrupt after an unexpected power cut
Cause: Writes in progress when power was lost — Fix: Run the file system check, restore from backup, and consider a small uninterruptible power supply for a desktop in an area with poor supply.
Many files corrupt across different folders
Cause: Failing drive, failing memory, or malware — Fix: Back up what still reads, then test the drive and the memory. Do not spend time repairing individual files until you know the hardware is sound.
Questions people ask
Can a corrupted file always be repaired?
No, and claims otherwise are marketing. Structural damage is often repairable; missing data is not. The realistic plan is to find another copy.
Why did it corrupt in the first place?
Most commonly an interrupted write — a removable drive pulled out, a network drop while saving, a crash, or a power cut. Next most common is a failing drive. Occasionally software with a bug in its save routine.
Does antivirus cause this?
Occasionally, when a scanner interferes with a file being written, and rarely with modern software. It is worth considering if a specific program's files are repeatedly damaged and nothing else is.
How do I stop it happening again?
Do not save directly to a removable drive or over a flaky network — work locally and copy afterwards. Eject drives properly. Keep backups with version history, which turns corruption into an inconvenience.