via email
Create the file fingerprint
Your browser creates a SHA-256 hash, a unique fingerprint for the file. The file is not uploaded.
ProofStamp a photo or file by email.
No upload. No account. Your device does the math.
Choose photos or files
Pick up to 5. Preview your selection before you ProofStamp it. Files stay on this device.
On phone: use Photos & videos for your gallery. For PDFs or documents, look for Files, My Files, Documents, or Browse. You may need to swipe the picker choices.
See file fingerprint (SHA-256)
This looks like a file created while the picker was open. Your phone may not have saved it to Photos or Files. Save the original before continuing.
What are these files for?
ProofStamp ready
Your ProofStamp is ready. Email it, save it, or copy it.
Your email app will open with it ready to send.
Optional: attach the originals before sending.
If you email the ProofStamp, attach the original files in your email app before you send it.
ProofStamp · v0.4.16Saved locally
The SHA-256 hash is the file's unique fingerprint. The same hash later confirms the file has not changed.
No connection? Save or copy the ProofStamp now. You can email it later.
Keep the exact original files.
You will need them if you want to check the ProofStamp later.
Check a ProofStamp
Choose the saved files and paste the ProofStamp. Everything is checked on this device.
Looking for a document? Choose Files, My Files, Documents, or Browse in your phone's picker.
How local verification works
ProofStamp calculates SHA-256 twice: once with your browser’s built-in cryptography and once with a separate Rust-based implementation. Both hash the same file bytes. If they disagree, verification stops. This helps catch calculation or runtime errors. Both checks still run inside this ProofStamp web app.
How it works
Your device creates the proof. Your email keeps it.
Keep the ProofStamp
Email it, copy it, or save it as a text file.
Check later
A matching fingerprint confirms the file has exactly the same contents.
What a ProofStamp does not prove
It does not prove when or where a file was created, who made it, whether it was edited before the ProofStamp, or whether its contents are true. The email received time shows when the ProofStamp reached that inbox.