Learn
Understand the proof before you need it.
Learn how an exact file can be checked later, what time evidence adds, and where its limits are.
Start here
From a saved file to a checkable record.
Three short reads: when proof matters, how a hash works, and which ProofStamp to use.
01 / A practical example
How to prove a photo or document existed before a specific date
A saved photo or PDF may matter months later. See how to preserve a record you can check again.
02 / How it works
What is a hash function? SHA-256 explained
See how SHA-256 identifies exact file contents. Change some text or try your own file in the interactive experiment.
03 / Choose a method
Which ProofStamp should you use?
Compare email receipts, independent timestamps and blockchain methods. Each gives you a different kind of evidence.
Further reading
Latest from ProofStamp.
Recent articles about records, independent verification and the situations where they matter.
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What If AI Had to Prove It Did the Work?
Read article →: What If AI Had to Prove It Did the Work?Anthropic’s new research could change how we verify AI-generated answers and the work behind them. You ask an AI to review some software code. It comes back with a reassuring answer: “No…
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Why Would a Nonprofit Publish Proof Nobody Asked For?
Read article →: Why Would a Nonprofit Publish Proof Nobody Asked For?What if nonprofits voluntarily made their reports independently verifiable? A simple practice could give donors and the public another way to check important records.
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Legal Records Outlive Software. Their Proof Should Too
Read article →: Legal Records Outlive Software. Their Proof Should TooLegal-tech platforms already track files and audit histories. Could selected legal records carry independent time evidence that remains verifiable after leaving the original system?
Ready to try it yourself?
Choose a method for your file. Keep the original and the proof so you can check it later.