Hidden thumbnails: how a cropped photo can show what was cut out
Published 10 October 2026
Most photos from phones and cameras contain a second, smaller copy of the picture: a thumbnail, stored in the metadata so file browsers can show a preview quickly. You never see it as a separate image, but it's there in the file.
Thumbnails become a privacy problem when a photo is edited. If you crop out a face, a name or a house number, the photo changes, but some apps leave the old thumbnail as it was. Anyone who extracts it then sees the original, uncropped scene, at a small size but often clearly enough.
How it happens
A photo's metadata is separate from the picture. An app that edits the picture has to decide what to do with the metadata: update it, remove it, or copy it unchanged. Most current photo editors make a new thumbnail or drop it. But apps that copy metadata without looking at it, older software and some quick editing tools keep the original one.
There are other kinds of embedded images too:
- Large previews saved by cameras, often near full size.
- Extra images some phones save after the main picture, such as depth maps and HDR gain maps.
- Motion photo videos, a short clip appended to the photo by some phones.
- Thumbnails of the original inside Content Credentials, which can show the image an edited one was made from.
Check a photo
Open it in our inspector. Under "Embedded thumbnails and previews" it shows every embedded image it finds, side by side with its size.
It also compares shapes. A thumbnail with a different shape from the photo (say, wide when the photo is square) was almost certainly made before the photo was cropped, and the report flags it: "A thumbnail that may show what was cropped out". When the metadata records the original size and it differs in shape from the image, the report says the photo was cropped.
A thumbnail with the same shape can still be outdated if something was removed without cropping, such as a blurred face, so look at it too.
Remove it
The cleaner removes embedded thumbnails and previews with the rest of the metadata, or on their own: choose "Choose what to remove" and tick "Embedded thumbnails and previews". The photo itself isn't recompressed.
HEIC photos from iPhones are the exception: their thumbnail is part of the file's structure, and the cleaner keeps it. HEIC thumbnails are made from the photo when it's saved, so they show the same picture.
Before posting a photo you've edited to hide something, check it, or remove all its metadata. If an edit really matters, also consider taking a screenshot of the edited photo: a screenshot is a new image with none of the original's data.