Symptoms
- Photo or video thumbnails appear in a folder or gallery app
- Clicking or opening the file shows an error or a blank/black screen
- File size shown is unusually small (a few KB) for what should be a photo or video
- Problem appeared after a recovery attempt, failed transfer, or drive error
Likely causes
- CommonThumbnail cache is separate from the actual file, and the full file is missing or corruptedOperating systems and photo apps store small thumbnail images independently of the original.
- CommonFile recovery only retrieved the thumbnail/cache data, not the original fileThis happens when the original file's data has already been overwritten but its thumbnail cache survived.
- PossibleFile transfer was interrupted, copying only a partial fileA partial file can be just large enough to generate a thumbnail before failing to open.
What to do
- Check the actual file size; a photo showing only a few KB is almost certainly just a thumbnail, not the full image.
- Search the original source device or drive again for the full-size file before assuming it's gone.
- If this followed a recovery attempt, try a different recovery tool, since results vary by software.
- Check for a separate thumbnail cache file (like Thumbs.db on Windows) which is not usable as a real photo.
- If a backup or cloud sync exists, check there for the original full-resolution file.
- If only thumbnail-sized data exists everywhere, the original file content has likely been overwritten and isn't recoverable.
Tools and parts
- File recovery software
When to call a pro
If full-size files can't be found anywhere and the source media may still have recoverable data, a data recovery professional can attempt a deeper scan.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.