What Facebook does to a picture
An image posted to Facebook is not the image the poster selected. It is resized to fit the platform's own dimensions, re-encoded with its own compression settings, and stripped of the metadata the original file carried.
All three of those matter here. Resizing throws away pixel detail, re-encoding replaces the original compression fingerprint with Facebook's, and stripping metadata removes any Content Credential that might have settled the question in one step.
The practical effect is that every image on the platform has been pushed slightly toward the middle of the scale. Genuine photographs score higher than they would as originals, and generated images score lower, which compresses the gap between them.
None of this is Facebook behaving badly. Recompression is what makes a site with billions of images load quickly, and metadata stripping is a privacy protection that removes location data most people would not want published. It is simply a cost that lands on verification.
Getting the best available copy
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Open the photo itself, not the post
Click the image so it fills the viewer. The version in a feed is a smaller preview than the one the viewer loads.
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Save the image file
Right click and save, or use the download option where the post allows it. This gets you Facebook's stored copy rather than a re-render of your own screen.
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Do not screenshot
A screenshot re-encodes the picture a second time using your own device's settings, on top of what the platform already did.
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Look for the original elsewhere
If the same picture appears on a personal site, a news page or a photographer's portfolio, that copy has usually been through less processing.
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Then run the check
Drop the saved file in and read both the score and the region map.
The bottom two rows are the ones that generate false alarms. A picture that has been screenshotted and re-shared twice can cross the decision line while being an entirely ordinary photograph, and the score is measuring the journey rather than the origin.
Reading the result on a platform image
Adjust your expectations rather than your conclusions. On a file that has been through a social platform, treat the middle of the scale as genuinely uninformative rather than as a weak signal in either direction.
The two ends still carry meaning. A score below twenty on a recompressed file is strong evidence of a photograph, because compression pushes upward and it did not. A score above eighty-five has survived a process that works against it, which makes it more meaningful, not less.
The region map holds up better than the headline number here, because a localised replacement stays localised through recompression even as the absolute values drift. One tile standing well clear of its neighbours is still a finding on a degraded file.
| Score | On an original | On a platform copy |
|---|---|---|
| Under 20 | Photograph | Photograph, more confidently |
| 20 to 45 | Photograph | Probably a photograph |
| 45 to 65 | Uncertain | Uninformative, ask for the original |
| 65 to 85 | Probably generated | Uncertain, get a better copy |
| Over 85 | Generated | Generated, more confidently |
The checks Facebook itself gives you
The platform carries context a detector cannot. When the post was made, whether the account has a history, whether the same image appears on other pages, and whether the picture is labelled by the platform as AI-generated.
That labelling is worth understanding. Where a generator embeds a marker that the platform reads, a label may appear automatically, and it is a strong positive signal when present. Its absence proves nothing, because most images arrive with no marker at all.
Post history is the check people skip and should not. A photograph posted three years ago, with comments from people who were there, is corroborated in a way no pixel analysis can match. A picture posted an hour ago by an account created last week is not.
When the picture is of somebody you know
The most common reason people check a Facebook photo is that it shows a person they recognise doing something that seems out of character. That case needs the region map rather than the score, because the frame is mostly a real photograph.
It also needs restraint. A high score on a picture of a named individual is not something to post in the comments. It is a reason to ask the person, or to report the post, and to keep the conclusion to yourself until somebody with more information has looked.
Groups, marketplace and shared posts
The context around a Facebook image changes how much the check is worth. A photograph in a community group, posted by a member with a history, sits in a very different evidential position from one in a marketplace listing by an account with no reviews.
Marketplace is where a check earns the most. Listing photographs are frequently taken from elsewhere, and a generated product image is now cheap enough that it appears in listings for goods that do not exist. Run the check, then run a reverse image search, because the stolen-photo case is more common than the generated one.
Shared posts are the weakest case of all. Each share is another opportunity for the image to be screenshotted, cropped or re-uploaded, and by the third hop you are analysing a copy that bears little pixel-level resemblance to what was originally posted.
Where a post has travelled, the useful move is to find the earliest version rather than to check the one in front of you. A reverse image search usually surfaces it, and the original will give a far more reliable reading.