Repair a corrupted JPEG: what is actually recoverable, and the thumbnail almost nobody tries

Before installing anything, it is worth knowing that corrupted covers two very different situations, and only one of them is fixable. Telling them apart takes a couple of minutes and decides whether repair software is worth buying at all.

First, look at the first bytes

Every JPEG begins with the marker FFD8 and a complete one ends with FFD9. That single fact is enough to sort most cases:

# first and last bytes
xxd broken.jpg | head -1
xxd broken.jpg | tail -1

Starts with FFD8, no FFD9 at the end. The file is truncated: the copy stopped, the card was removed, the transfer was interrupted. The data that made it through is intact. This is the most recoverable case, and it is why such photos often display normally down to a certain height and then turn grey or green.

Does not start with FFD8. The header is damaged, or the file is not a JPEG despite its extension. Repair is possible in some header-only cases, but the odds drop sharply.

Starts and ends correctly but still will not open. The damage is inside the image data. Partial rendering is sometimes possible; a faithful reconstruction usually is not.

The thumbnail almost nobody tries

This is the step worth knowing before you pay for anything.

Most cameras and phones write a small preview image inside the EXIF metadata, near the beginning of the file. Because it sits before the main image data and is a fraction of the size, it very often survives corruption that destroyed the full photo.

exiftool -b -m -ThumbnailImage broken.jpg > thumb.jpg

The -b flag asks for binary output and -m tells ExifTool to ignore minor errors, which matters because the file is damaged by definition. If there is no embedded thumbnail, the output is empty and you have lost nothing but a few seconds.

Be clear about what this gives you: a small image, typically a few hundred pixels wide, not a printable photograph. But when the alternative is a file that opens on nothing, getting back a recognisable version of a photo is often the difference between losing a memory and keeping a trace of it.

What repair tools actually do

They rebuild the container, not the content. A tool can restore a missing header, close a file that has no end marker, or re-encode the recoverable portion into a valid image. That genuinely works on truncated and header-damaged files.

What no tool can do is invent bytes that were overwritten. If another file was written over that area of the disk, the original data is gone, and any product promising otherwise is selling a result it cannot deliver. This is the same honesty line as our guide on repairing a corrupted video file: the container is fixable, missing data is not. A spreadsheet is a different case again, because an .xlsx is a ZIP container you can open and inspect: see repairing a corrupted Excel file.

If the photo is gone rather than broken

The two problems get confused constantly, and the tools do not overlap.

Repair applies to a file you still have, whose contents are damaged. Recovery applies to a file that was deleted, formatted away or lost with a card, where the job is to find the bytes on the device before something else overwrites them. For that second case, carving is the right approach and our TestDisk and PhotoRec guide covers it, as does the walkthrough on recovering photos from a corrupted SD card.

One rule applies to both: stop writing to the storage device immediately. Every new file reduces what can still be recovered, and that includes installing recovery software onto the same drive.

The short version

Check whether the file starts with FFD8 and ends with FFD9, because a truncated JPEG is the most repairable case by far. Try the embedded EXIF thumbnail before anything else, since it costs nothing and often survives when the main image does not. Understand that tools rebuild structure and cannot recreate overwritten data. And if the file is missing rather than damaged, you need carving, not repair.