Overview
CommitProof is a service that helps you prove a piece of text or a file existed at a specific moment, without ever revealing what it actually says. It is built for inventors, designers, writers, and founders who want a low-cost public timestamp for "what I knew, when" before sharing an early draft, sketch, or business idea. The original content never leaves your device, so your secret stays a secret while the proof becomes public1.
CommitProof runs on the Cardano blockchain, a public ledger anyone can read but no one can quietly rewrite. The service is a single-operator project from Tommy Kammerer in Neuried, Germany2, and is listed in the official Cardano apps directory under the Notary category3. The site ships in English, German, Japanese, and Spanish.
Key Features
- Public proof of when something existed. Each CommitProof entry records a short fingerprint of your content (a one-way code that changes if even one character changes) on Cardano. The block timestamp on the blockchain serves as the proof of time, which anyone can later check4.
- Your content never leaves your browser. The fingerprint is created on your own computer using your browser's built-in cryptography tools. The fingerprint is mixed with a random scramble code, and only that fingerprint goes to the blockchain, so CommitProof never sees the underlying file or text1.
- Pay with ADA or a card. Each proof costs 3 ADA plus the standard Cardano network fee (around 0.18 ADA). Payment works from a Cardano wallet, including Eternl, Lace, and Typhon, or with a credit card, Apple Pay, or Google Pay. No subscription, no account1.
- Downloadable proof file you control. Every CommitProof entry produces a PDF and a small data file containing the transaction reference, your original text (or, for a file, only its file details), and the scramble code1. To verify a file proof later you also need the original file, so keep it safe5. You keep these locally to verify the proof later or share the record if a dispute comes up4.
- Public proof index anyone can audit. One shared CommitProof address on Cardano receives every proof transaction, and the site's Proof Explorer lists them, so activity is visible to anyone who wants to look4.
What to Expect
A first-time visitor sees a homepage that leads with two buttons, "Create Proof" and "Verify." Creating a proof is a short in-browser flow, where you type the text or pick a file, confirm a 3 ADA payment, and download the resulting PDF and data file. There is no email signup and no account.
Verification works the same way in reverse. Upload the proof file (or paste the transaction reference, original text, and scramble code), and the site recreates the fingerprint and compares it to what is stored on the blockchain. The whole experience is one short page each way, and the FAQ explains every step in plain language, including how to confirm in your browser's developer tools that your content really never gets uploaded1.
CommitProof is a paid utility on top of Cardano transaction notes, with the operator named in the site's legal notice2 and its hosting, payment and blockchain-data providers (Cloudflare, Stripe and Koios) listed in its privacy policy6. The FAQ also collects the legal background for blockchain timestamps, citing the EU eIDAS Regulation, a 2025 French court ruling7, and rules issued by China's Supreme Court in 20188. The site is explicit that a timestamp is supporting evidence, not a replacement for a patent or copyright registration.
