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Evidence mode

Short answer: with Evidence mode on, every export carries the page address, the exact capture time with time zone and a SHA-256 checksum of the pixels, on the image and inside the file; anyone can verify the file later at /verify/ without uploading it. It proves the picture is unchanged, not what the clock said. Pro.

A screenshot is easy to alter, which is why one is rarely enough on its own. With Evidence mode on, every export carries a band with the page address, the exact time of the capture and a SHA-256 checksum of the pixels, and the same facts are written inside the file. Anyone can drop the file on the verify page later and see whether it has changed since. Part of Pro.

Updated September 28, 2026By the FullPage Capture team, the people who build the extension

How it works

  1. Turn Evidence mode onRight-click the extension icon, open Options, and switch on Evidence. It stays on until you switch it off.
  2. Capture as usualClick the icon or press Alt+Shift+K. Every export from now on carries the band: PNG, PDF and clipboard copies alike.
  3. Verify, whenever, by anyoneDrop the file on the verify page and it reads the address and time from the file and recomputes the checksum in the browser; nothing is uploaded. A short Python recipe on the same page does it offline.

What the file carries

  • The page address, as it was in the address bar.
  • The exact time of the capture, with its time zone, from the capturing computer's clock.
  • A SHA-256 checksum of the pixels above the band.
  • The same facts inside the file: text chunks in a PNG, the Info dictionary in a PDF, so they survive renaming and travel with the file.
  • Lossless storage: images are always PNG and PDF pages embed the picture losslessly, so the checksum can be recomputed from the file itself.

What it proves, and what it does not

It proves that the picture is unchanged since the capture: recompute the checksum from the file and compare.

It does not prove what the computer's clock said at the time, or what the page looked like to anyone else. The time comes from the capturing machine. Present it as what it is: a capture whose integrity can be checked, with the address and time the capturing computer recorded.

Who uses it

  • Support and QA teams attaching a page to a ticket that may be questioned later.
  • Compliance and content teams keeping a record of what a page said on a date.
  • Anyone documenting a listing, an offer, a message or a review that might change or disappear.

Questions

What exactly is on the band?

The page address, the exact time of the capture with its time zone, and a SHA-256 checksum of the pixels above the band. The same three facts are written inside the file: as text chunks in a PNG, in the Info dictionary of a PDF.

What does the checksum prove?

That the picture is unchanged since the capture: recompute it from the file and it either matches or it does not. It does not prove what the computer's clock said, or what the page looked like to anyone else; the time comes from the capturing machine. Say so when you present it.

Why is the image always PNG in Evidence mode?

JPEG re-encodes the pixels, which would change the checksum. Evidence-mode images are saved as PNG, and PDF pages embed the picture losslessly, so the checksum can be recomputed from the file itself later.

Can someone verify the file without the extension?

Yes. The verify page works in any browser and uploads nothing, and the Python recipe on it needs only the file. Both read the facts from the file and recompute the checksum. The verify page

Does the band go on clipboard copies too?

Yes, and clipboard copies made in Evidence mode are never resized, so the checksum stays valid after pasting.

Is Evidence mode a substitute for a notary or a forensic tool?

No. It gives you a capture whose integrity can be checked by anyone, with the address and time attached. Whether that is enough depends on who is asking and for what; for a dispute with a customer or a bug report it usually is, for a court it is one piece of evidence among others.

Is it free?

Evidence mode is part of Pro: Try Pro: $0 for 7 days, then $19 a year. Verifying a file is free for everyone, always. See Pro

Try it on the page you are reading. Free, no account, no watermark. Nothing is uploaded.

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