What is OpenTimestampsA free, open-source way to anchor a file’s fingerprint to Bitcoin

TimeBinder adds a layer of protection against AI and human fraud and disputes.

The file stays on your device. Your browser makes a digital fingerprint of the file. TimeBinder records the fingerprint and the time, not the file.

Short answer

OpenTimestamps is a free, open-source protocol that anchors a file’s cryptographic fingerprint to the Bitcoin blockchain, so the file can later be shown to have existed by that time. It is usually used through command-line or developer tools, and it does not show who made the file.

How it works, in plain terms

You make a SHA-256 fingerprint of a file (see what is a file hash). OpenTimestamps sends that fingerprint to calendar servers, which combine many fingerprints into one tree and anchor the result in a Bitcoin transaction. You keep a small proof file that, once the transaction is confirmed, lets anyone check the file against the blockchain without trusting a company.

The project is documented at opentimestamps.org. It is open source and free to use. Many people find the command-line tools hard to use, and the proof files need to be stored safely.

How TimeBinder relates

TimeBinder is a separate service that also anchors fingerprints to Bitcoin, with a browser app, certificates and pricing. A TimeBind records a SHA-256 fingerprint of the exact file and a time, anchored to Bitcoin. The fingerprint is made in your browser and the file is not uploaded. Which one suits you depends on how comfortable you are with command-line tools and what you want in a record. See OpenTimestamps alternatives for a side-by-side view.

Either way, a timestamp shows an exact file existed by a time. It does not show authorship, ownership or legal outcome.

Make a TimeBind: first one free →

First Pooled TimeBind free, no card, then from US$5. An ASAP TimeBind is US$15.

Frequently asked questions

Is OpenTimestamps free?

Yes. It is open-source software and a free-to-use public service. Check the project site for current details.

Do I need to keep the proof file?

Yes. The proof file is what lets you check the original file later, so keep it safe along with the original file.

Is TimeBinder built on OpenTimestamps?

No. TimeBinder is a separate service that records fingerprints and anchors them to Bitcoin in its own way.

Does an OpenTimestamps proof show who made the file?

No. It shows that a file with that exact fingerprint existed by the time of the Bitcoin anchor.

Sources

OpenTimestamps, opentimestamps.org.
TimeBinder, OpenTimestamps alternatives.

Related guides and tools

Your file’s fingerprint, anchored to a global network secured by real electricity and cryptography.

Editing a file—including with AI—changes its fingerprint, not its existing network record.

How this works

Your file’s SHA-256 fingerprint, a short code worked out from its exact contents, is made in your browser, and the file itself stays on your device. A cryptographic commitment to that fingerprint, which may be combined with others, is then anchored in a block on the Bitcoin blockchain. Bitcoin is secured by proof of work: computers around the world spend real electricity to add each block, and changing an earlier block would mean redoing that work faster than the rest of the network. Until that block is confirmed, your proof is pending. Once the Bitcoin anchoring is confirmed, you can verify the proof against that recorded commitment. The confirmed record can then be checked; Pooled TimeBinds are checked through TimeBinder, while ASAP TimeBinds can also be checked independently. If you check the file later and its fingerprint still matches, that shows the file existed no later than the recorded time. The record doesn’t show who made the file, whether AI was used, or that its contents are true.

Your filestays on your device
FingerprintSHA-256
Network timestampon Bitcoin

Record a fingerprint of the file you rely on

Add a layer of protection against AI and human fraud and disputes: a dated, checkable record of the exact file you hold.

Open the app and sign in with email or Google.
Add your files. They stay on your computer.
Seal them and download your Proof of Time certificates.

Open TimeBinder →

First Pooled TimeBind free, no card, then from US$5. See pricing.