Screenshots are worth taking. They preserve the things a downloaded file strips away: what the listing said, what it was priced at, which account posted it, what the caption claimed. When a page comes down an hour after you found it, the screenshot may be the only record that it existed at all.
The trouble starts when a screenshot is asked to carry more than that.
It records context, not priority
Showing that someone copied your work involves two separate questions, and a screenshot is only adjacent to either.
The first is whether your work existed before theirs. That’s a question about your record. A registration made before the copy surfaced speaks to it; an image of the copy doesn’t, however many you take.
The second is how alike the two works actually are. Answering that means examining both together. A photograph of one of them isn’t an examination.
So a screenshot establishes that at some point, something resembling your work was visible somewhere. Useful, and a long way short of what people assume they’re holding.
Why it carries so little on its own
The timestamp is whatever the device reported and takes seconds to change. A URL visible in the frame is pixels in a picture. And the file is an image, editable with software that ships on every computer.
Your screenshot isn’t fake. But nothing about it distinguishes it from one that is, and that’s the whole difficulty.
What to do with the ten minutes instead
Register the work before it goes out. This is the only part that has to happen in advance, and it’s why registration works better as a habit than as a response.
When you find a copy, download it rather than photographing it. Then compare your registered work against what you obtained. A comparison documents where the two align, which is what you wanted the screenshot to demonstrate in the first place.
Check your infringement docket too, where flagged matches and infringement reports appear. Dacr compares each registration against everything already registered with Dacr, automatically, so a match involving work someone else has registered may already be sitting there. No screenshot required, and nothing to switch on.
Keep the screenshot anyway
It’s a note to yourself about what you saw and where, and that note has a way of mattering three months later when nobody can remember which account the listing belonged to.