Timestamp your documents without disclosing them.
Signed contract, minutes, report, specifications: inscribe the document’s SHA-256 fingerprint on the Bitcoin blockchain. Its date and integrity become verifiable forever — while its content never leaves your computer.
A fingerprint rather than a document
SHA-256 hashing turns any file — a one-page PDF or a one-gigabyte archive — into a unique 64-character fingerprint. It is this fingerprint, and only this fingerprint, that is inscribed.
Confidentiality by design
The fingerprint is computed in your browser via the Web Crypto API. The file is sent neither to btc3r nor to the network: it is mathematically impossible to reconstruct the content from the hash.
Verifiable integrity
The same document always produces the same fingerprint; a single changed byte produces an entirely different one. Comparing two fingerprints is enough to prove that a document has remained intact.
Certain date
Once the fingerprint is included in a Bitcoin block, the block’s timestamp is authoritative: no one — not you, not btc3r, not anyone — can backdate or alter it.
What professionals timestamp
Whenever a document commits, protects or records, its exact version on a given date has value.
Contracts, amendments, signed quotes
Freeze the signed version of a contract or an amendment. In case of a later disagreement over “which version was authoritative”, the fingerprint settles it instantly.
Minutes & decisions
General-meeting minutes, committee reports, management decisions: timestamp the final document at the moment it is adopted.
Logs, incident reports, datasets
Technical logs, audit reports, data exports: prove they have not been altered after the fact — often a decisive point in a dispute.
Specifications & deliverables
Timestamp the approved specifications and each deliverable submitted: the agreed scope and the delivery dates become indisputable.
Timestamp in four steps
Less than two minutes on your side; the block confirmation does the rest.
Drop in the file
On the inscription page, select your document. It is read locally by your browser, with no transfer.
The fingerprint is computed
The file’s SHA-256 appears: 64 characters that identify your document down to the bit.
Inscription on Bitcoin
The fingerprint is inscribed in a transaction, broadcast to the network, then confirmed in a block.
Certificate & archiving
You receive the certificate (TXID, block, timestamp). Archive it with the unchanged original document: together, they make the proof.
Blockchain timestamping and qualified timestamping
The European eIDAS Regulation (No 910/2014) distinguishes “simple” electronic timestamping from “qualified” timestamping, issued by a qualified trust service provider and benefiting from a presumption of accuracy. A Bitcoin inscription falls into the first category: it does not have the qualified presumption, but article 41 of the Regulation prohibits denying it any legal effect solely because it is not qualified. In practice, it brings two guarantees that no provider can offer alone: an unlimited period of verifiability and total independence — the proof remains verifiable even if btc3r or any other intermediary were to disappear. For the most sensitive matters, the two approaches usefully combine.
Timestamping: what people ask us
Is my document transmitted to btc3r during timestamping?
No, never. The SHA-256 fingerprint is computed locally, in your browser, using the Web Crypto API. Only this 64-character hexadecimal fingerprint is transmitted and then inscribed: the document stays on your machine, and its content cannot be reconstructed from the fingerprint.
What exactly does a blockchain timestamp prove?
Two things: that an exact content existed no later than the block’s date (the certain date), and that this content has not changed since (integrity, verified by recomputing the fingerprint). It does not prove who held the document nor the legal validity of its content.
Is it a qualified timestamp within the meaning of the eIDAS Regulation?
No. A qualified eIDAS timestamp requires a qualified trust service provider and enjoys a presumption of accuracy (article 41 of Regulation No 910/2014). A blockchain timestamp does not have this presumption, but the same article prohibits setting it aside solely because it is not qualified: it remains admissible as evidence, assessed by the judge.
If I change the document after timestamping, what happens?
The new version produces a completely different fingerprint: the timestamp only applies to the exact version that was hashed. This is precisely what gives the mechanism its value — and why the original version must be kept unchanged. To date a new version, simply make a new inscription.
Can I timestamp several documents in a single inscription?
Yes: group them into an archive (zip, tar) and inscribe the archive’s fingerprint. The proof will then apply to the whole set, provided you keep the exact archive. For volume or recurring needs, btc3r offers tailored pricing.
Other ways to use inscription
Proof of anteriority
Date a creation — manuscript, invention, code — before showing it to the world.
Learn more →Proof of existence
Show that a file existed on a given date, verifiable by any third party.
Learn more →Understand inscription
OP_RETURN, SHA-256, independent verification: the foundations explained simply.
Learn more →The authoritative version, dated forever.
Timestamp a document for 9.60 € : fingerprint computed in your browser, inscribed on Bitcoin, verifiable without us.