Use the exact file
The file must be the same one that was protected, byte for byte. That is why the verification ZIP is the safest option.
Verify
Check a Sellat proof.
Add the file or the verification ZIP you want to check. Sellat will tell you whether it matches a protected proof exactly.
What verification checks
An exact match, not a resemblance.
Verification compares the SHA-256 fingerprint of the file you upload against the protected fingerprints. It does not look at content or file name.
Re-exporting changes the fingerprint
Opening and re-saving a photo or PDF can produce a different file. It will look the same, but its fingerprint will differ.
No account needed
Anyone can verify a file, whether or not they are connected to whoever created the proof.
Frequently asked questions
Before you ask.
Why can verification fail if I use a loose copy of the file?
When verifying, the file must be exactly the same as the one that was sealed. Some phones and programs like Word, Acrobat or photo editors can convert files, recompress images or change metadata when opening them. Even if they look visually the same, the hash changes and no longer matches. That is why we recommend verifying with the Sellat ZIP: renaming it, moving it or re-compressing it does not affect the proof; modifying the sealed file does.
What does the Sellat verification ZIP contain?
The exact file that was sealed (in the "original" folder), the PDF certificate and a README with the instructions to check it. Once the batch is anchored the package also carries proof.json — the portable proof with the Merkle path — and, where they exist, the OpenTimestamps Bitcoin proof and the qualified timestamp. To check the proof, upload the full ZIP to sellat.app/en/verify and select “Sellat ZIP”.
Can I verify without being a customer?
Yes. Anyone, at any time, can go to sellat.app/en/verify and check whether a file matches a certificate. No account, no payment, nothing.
Which file should I keep as proof?
Keep the Sellat ZIP: its "original" folder holds the exact version that was sealed, and that is what lets you check the proof. Bear in mind that a screenshot, a format conversion or forwarding through an app that recompresses images produces a different file with a different fingerprint. Your Sellat record still exists, but checking it needs the exact version, not the transformed copy. On mobile devices, especially iPhone, a photo can be converted when shared; in PDFs and documents, Word or Acrobat can rewrite metadata even if the file looks visually the same.