Cropped to hide the card number in the corner. This is an illustration — no real file, name or location is used.
Before — what you would be sending
receipt-cropped.jpgJPEG
Embedded preview imageThe pre-crop frame is still inside the file
Exact location51.503364, -0.119543
SoftwareAdobe Photoshop 26.0
Cropped at 21:04 · original frame written at 20:58
After cleaning
receipt-cropped-clean.jpgJPEG
Embedded preview imageremoved
Exact locationremoved
Softwareremoved
The crop you made stays. The old preview that undoes it does not.
The thumbnail nobody thinks about
Cameras write a small preview into the file so gallery apps can show it instantly without decoding the full image. It lives in a second directory of the EXIF block. Some editors update it when you crop. Plenty do not, and simply leave the old one in place.
This has gone wrong publicly, more than once
The pattern is always the same: someone crops a screenshot or photo to hide a detail, publishes it, and the embedded preview still contains the uncropped frame. It is recoverable by anyone who opens the file with a tool that reads EXIF, which is to say, anyone who cares to look.
Redaction by drawing over it is a separate trap
Pixelation is the risky one: where the hidden content is text in a known font, researchers have reconstructed it by searching for the rendering that pixelates to the same blocks. A heavy blur on a photograph is far harder to undo and often practically safe. Solid black is safer still, but only if the image is then flattened and re-exported — in a layered file or a PDF, the covered content usually still sits underneath, fully intact.
How to be sure
Drop the file in above. If a preview is stored inside, this page will render it on screen so you can see exactly what a recipient could recover. Cleaning removes it along with everything else.
In practice
Which editors regenerate the thumbnail
There is no rule, which is the difficulty. Desktop editors from major vendors generally rewrite the preview on save. Quick crops in a phone gallery, in a messaging app, or in a lightweight web tool frequently do not, because regenerating a thumbnail costs processing time for something nobody looks at. You cannot tell by looking at the result. The only reliable check is to open the finished file and see what preview it contains, which is what the tool above does.
A safer routine for hiding part of a picture
Crop the image, then export it as a new file rather than saving over the original. Exporting builds the file fresh, which usually rebuilds the preview along with it. If the detail you are hiding matters — a card number, a name badge, a screen — the safest sequence is: crop, export, reopen the exported file, and check that. Three steps, and it removes the entire category of problem.
Why pixelation specifically is risky
Pixelation replaces a block of pixels with their average colour. That is a deterministic transformation, so where the hidden content is text in a known font at a known size, an attacker can render every candidate string, pixelate each one the same way, and look for a match. Published research has recovered redacted text this way. Blur on a photographic subject is much harder to reverse because there is no small set of candidates to test against. Neither is as good as cropping the content out entirely and exporting a new file.
Common questions
Can a cropped photo be uncropped?
Sometimes. If the file still holds an embedded preview written before the crop, that preview shows the original framing.
Is blurring safe for hiding text?
Pixelation of text is the least safe, since it can sometimes be reconstructed. Heavy blur is harder to undo. Neither is as reliable as cropping the content out and re-exporting.
Does taking a screenshot of a photo remove the metadata?
It removes the original EXIF, yes, because the screenshot is a new image. It also adds its own, and on some systems that includes the device name.