A screenshot as proof
A picture of a page is offered as evidence that the page said something. It is evidence that a picture exists.
Bucket: NEVER
A screenshot cannot be verified. There is no signature over it, no way to bind it to a moment, and no way to establish that the thing depicted was ever on a screen anywhere. Editing one requires no skill and leaves no trace you can check.
Why it is categorically false rather than just weak
Weak evidence still points somewhere. A screenshot does not, because the cost of producing a convincing false one is the same as the cost of producing a true one. When both cost the same, the artefact carries no information about which you are holding.
Compare with a signed message. Producing a false one requires the private key, which is expensive in the specific sense that nobody has it. That asymmetry is what makes evidence evidence.
Where this shows up
- A screenshot of a market front page as proof that an awazon working link is live.
- A screenshot of a wallet balance as proof of a payment.
- A screenshot of a message as proof of what somebody said.
- A screenshot of a dispute outcome as proof of how disputes go.
- A screenshot of an address as the way an address gets passed along.
The last one is the worst, and not for the obvious reason. It cannot be copied, so it has to be retyped, and retyping is where characters get changed. An address delivered as an image is an address that will be entered by hand.
The subtler failure
Even a completely genuine, unedited screenshot proves nothing useful, because it has no time attached. A real picture of a real page from eight months ago looks the same as one from this morning. The file timestamp is metadata, and metadata is a text field.
So the honest reading of a screenshot is that somebody at some point had a screen that looked like this, probably. That is almost never the claim being made with it.
What people get wrong
They look for editing artefacts. Compression noise, misaligned text, wrong fonts. Sometimes those are there and finding one settles the question. Not finding one settles nothing, because the easiest way to make a convincing screenshot is not to edit an image at all. It is to change the page in your own browser and then take a real picture of it.
The reasonable use
Screenshots are fine as illustration. Showing somebody where a button is, describing a layout, remembering what a page looked like. All of that is communication rather than evidence and none of it asks the image to prove anything.
The line is crossed the moment a screenshot is offered to settle a disagreement about a fact. At that point it needs to carry weight it cannot carry, and the person offering it is usually not aware of the switch.
What would move this
A capture format that signed the image together with a trustworthy timestamp and a statement of origin, verifiable by you. Schemes like that are being built for other reasons. If one were in use and you could check it, screenshots would become real evidence and this page would move to DEPENDS with the condition being whether the signature checks out.
Nothing like that is in use in this context, so the statement stands as written.