How to Prove a File Existed at a Specific Date

ProofStamper is a free online tool that creates certified timestamps for any file using the RFC 3161 standard. It proves a file existed at a specific date by generating a cryptographic proof verified by an independent Timestamp Authority — without uploading your file. Available in 10 languages, no account required.

You created something — a design, a contract, a piece of code, a photograph — and now you need to prove it existed before a certain date. Maybe a client is disputing your work, someone copied your creation, or you simply want a record for the future. The solution is simpler than you think: a certified timestamp can prove your file existed at a precise moment, verified by an independent authority — without uploading your file anywhere.

How certified timestamps work

A certified timestamp is a cryptographic proof that a specific file existed at a specific moment in time. It uses an international standard called RFC 3161, trusted by courts, auditors, and institutions worldwide.

  1. Your file is fingerprinted locally: A mathematical algorithm (SHA-256) calculates a unique fingerprint of your file — directly in your browser. The file itself never leaves your device.
  2. The fingerprint is sent to a Timestamp Authority: The fingerprint (not your file) is sent to an independent Timestamp Authority (TSA), which attaches a certified date and digitally signs it. Like a notary stamp — instant, free, 24/7.
  3. You receive a Proof Pack: You download a Proof Pack containing a PDF certificate and a cryptographic token (.tsr file). This proof is independently verifiable by anyone — even without ProofStamper.

Because only the fingerprint leaves your device, nobody — not ProofStamper, not the Timestamp Authority — ever sees, stores, or accesses your file. Your content stays private.

How to create a certified timestamp in 30 seconds

  1. Go to ProofStamper: Open proofstamper.com — no account, no signup, no installation.
  2. Drop your file: Drag and drop any file. It's fingerprinted instantly in your browser. Nothing is uploaded.
  3. Download your Proof Pack: Click "Create proof" and download your Proof Pack (PDF certificate + .tsr token). Done.

Frequently asked questions

Does my file get uploaded to a server?
No. Your file is processed entirely in your browser. Only a mathematical fingerprint (SHA-256 hash) is sent to the Timestamp Authority. ProofStamper never sees, stores, or has access to your file.
Can I timestamp any type of file?
Yes — documents, images, videos, code, audio, archives, databases. Any digital file can be timestamped.
Is it really free?
The basic certification is free, with a watermark on the PDF certificate. For watermark-free certificates and professional features, ProofStamper offers a Pro plan at $9/month and one-time credit packs.
How do I verify a timestamp later?
Upload your Proof Pack or your original file + .tsr token. The tool checks the cryptographic signature against the Timestamp Authority's public key. You can also verify manually using OpenSSL.
How is this different from DocuSign?
DocuSign proves someone agreed to something (consent). ProofStamper proves a file existed at a date (existence). Different problems. You might need both — but often, proof of existence is all you need.
What if ProofStamper shuts down?
Your Proof Pack is self-contained and independently verifiable using standard open-source tools (like OpenSSL). It does not depend on ProofStamper's continued existence.