How to Check If an Image Has Been Reused Without Permission

“That looks exactly like mine” needs a second step

A reverse image search or a tip from a colleague gets you to a suspected match, not a confirmed one. Two images can look alike at a glance and be genuinely different files, and a real copy is often altered just enough — recompressed, cropped a little, color-corrected — that a side-by-side glance doesn’t settle it either way. Before you act on a suspected reuse, it’s worth actually confirming the visual match rather than going on impression.

This is a technical check, not a legal one. What follows tells you how visually similar two files are and, if they match, roughly what was done to the copy — resized, recompressed, cropped. It doesn’t establish licensing, fair use, or anything about permission; that’s a legal question with a legal answer, and a similarity score isn’t evidence of infringement on its own. Treat this as the step that tells you whether it’s worth pursuing further, not the last step.

Get the closest thing to the original

Save the suspected copy directly from the page (not a screenshot of it, if you can help it — screenshotting recompresses the image again and adds a generation of loss that isn’t in the original file). Then pull up your own original — the actual source file if you still have it, or the highest-resolution version you published if you don’t.

Compare them

Upload both to DiffALL’s image comparison. A high similarity score with a heatmap that’s mostly quiet — no significant hot regions — is a strong visual match: the same underlying image, possibly recompressed or resized, but not meaningfully altered in content.

If the images are different sizes, that’s expected for a reused image and not itself suspicious — a genuine copy is routinely resized to fit whatever layout it’s being used in. DiffALL’s feature-matching mode (on by default) detects matching keypoints between the two images and aligns one to the other before scoring, rather than assuming they’re already lined up — useful here since a resized or slightly cropped copy won’t sit pixel-for-pixel over the original.

A low score with heat concentrated at the edges usually means one version was cropped — check whether what’s missing is a watermark, a signature, or an attribution line along the border, which is a specific and common pattern worth noting separately from the general similarity number.

A low score with heat spread evenly across the frame more often points to a genuinely different image — similar subject, similar composition, but not derived from your file — rather than a copy with heavy edits. Don’t assume alteration when the more likely explanation is that it’s a different photo of a similar thing.

A moderate score with a color shift and nothing else is consistent with a recolor or a different compression pass on the same source image — content unchanged, presentation adjusted.

What this does and doesn’t tell you

It tells you, with a specific number and a picture of exactly where the two files differ, whether you’re looking at the same image or a genuinely different one — instead of relying on how confident you feel from memory or a quick glance. That’s a meaningfully stronger basis for whatever you do next.

It doesn’t tell you about licensing terms, whether the use falls under an exception, or what to do about it. If the match is confirmed and it matters enough to pursue, that’s the point to involve someone who actually handles this — a platform’s reporting process at minimum, legal counsel if the stakes justify it. A visual comparison tool answers “is this my file,” which is a necessary first fact and not the whole picture.

Try it

Compare images → — use the original file where you can, not a screenshot of a screenshot, and read the heatmap alongside the score rather than the score alone.