File corrupted after a USB pull, crash or sync

The file was fine yesterday. Then the laptop died mid-save, the USB stick came out too early, or OneDrive made a copy that won't open. What happened depends on how the file was damaged, and that decides how much comes back.

Three ways a file gets damaged

1. Cut short

The save or copy stopped part-way, so the file is smaller than it should be. Word and Excel keep the file's table of contents at the end, so it's the first thing lost, and they refuse the file even though most of it is fine. Usually very recoverable: everything before the cut can be saved.

2. A block of zeros

Part of the file was never written, so a stretch of it is just zeros. Sync tools and failing drives do this. The file is the right size but won't open. Often partly recoverable: the part before the damage comes back, and often text after it too.

3. All zeros, or 0 KB

Nothing was ever written. Not recoverable from that file. Look for another copy instead (see below).

Before anything else

Stop saving over the file, and make a copy of it to work on.
Check OneDrive or SharePoint version history, and Windows Previous Versions.
In Word, look in File → Info → Manage Document → Recover Unsaved Documents.
If the original is still on the USB stick, copy it from there again. The copy on your computer may be the broken one.

Recovering what's left

Office File Repair checks the file in your browser, tells you which kind of damage it has, and shows a preview of what can be recovered. Nothing is uploaded, and you only pay if you want the repaired copy.

Check your file: the preview is free