01
Your file stays yours
Fingerprinting happens in your browser. We receive a 64-character hash, never the document — nothing to leak, nothing to subpoena.
Blockchain notarization · proof of existence
Prove your document existed. Verify it without trusting us.
Drop a file and notaros seals its cryptographic fingerprint onto Base and Bitcoin — permanent, timestamped, and provable by anyone, forever. No account. Your document never leaves your device.
Notarize a document — $25
or drop a file below to fingerprint it free →
Fingerprint it yourself
SHA-256 · in your browser
Drop a document to fingerprint it
or click to choose — any file type · it never leaves your browser
document.pdf
— KB
Its SHA-256 fingerprint
…
Anchors to Base
Bitcoin · OpenTimestamps
Computed on your device. This 64-character fingerprint is the only thing notaros would publish — we never receive the file itself.
The point of notaros
Trust is the one thing we designed out of the product.
A notarization is only worth something if you don’t have to trust the notary. Every proof notaros issues can be checked against the public blockchain by anyone — including checked against us.
02
Anchored in the open
The fingerprint is written to Base and to Bitcoin via OpenTimestamps — public, permanent records that are ours to write but no one’s to alter.
03
Verifiable without us
Anyone can confirm a proof with a block explorer and an open tool. If notaros vanished tomorrow, your proof would still stand on its own.
How it works
Notarize a document in three steps — no account, no upload, no subscription.
01
Fingerprint your document
Your browser computes a SHA-256 hash of the file. Change a single byte and the fingerprint changes completely — and the original can never be reconstructed from it.
02
Anchor it to public blockchains
notaros writes the fingerprint to Base and submits it to Bitcoin through OpenTimestamps. The blockchains’ own timestamps become the independent, tamper-proof record that this document existed at this moment.
03
Receive a certificate you can prove alone
You get a signed PDF certificate, a hosted verifier, and a self-contained offline verifier you keep forever. Confirming a proof needs nothing from us — only the public record. See the full walkthrough →
Open standards
Built on records the whole world can read.
No proprietary format, no walled garden. Everything notaros produces resolves to public, documented standards you can verify with ordinary tools — or with our free open verifier.
SHA-256 fingerprints
Base anchoring
Bitcoin via OpenTimestamps
Client-side hashing
Open, downloadable verifier
Paid only in USDC / USDT stablecoins — no cards
Pricing
Pay only for what you seal.
No account to maintain, no monthly minimum, nothing stored on your behalf. One document, one payment. Full pricing →
Full service
$25 / document
The complete, court-minded record — for when a proof needs to stand entirely on its own.
- Anchored to Base and Bitcoin / OpenTimestamps
- Signed PDF certificate
- Hosted verifier page
- Downloadable offline verifier, kept forever
Programmatic — API · MCP · A2A · x402
$3 / anchor
Notarize straight from your product, pipeline, or AI agent — same anchors, same independent verification, delivered as a lean signed receipt.
- REST API with a full OpenAPI spec, plus MCP & A2A
- Signed JSON receipt +
.otsproof — no PDF - Bulk: one Merkle order, from $3/anchor, bulk to $0.15 — self-service
- Every price published — computed by
/quote, no account, no negotiation
Questions
What blockchain notarization actually gives you.
What is blockchain notarization, or proof of existence?
It is cryptographic evidence that a specific document existed at a specific point in time. notaros records a SHA-256 fingerprint of your file on public blockchains; because those records are permanent and independently timestamped, they show the document existed no later than that moment — without relying on anyone’s word for it.
Does notaros see or store my document?
No. Your file is fingerprinted with SHA-256 inside your own browser. Only the 64-character fingerprint is sent — never the document. There is nothing for us to read, store, leak, or be compelled to hand over.
How does someone verify a notarization?
They re-compute the file’s SHA-256 fingerprint and check it against the blockchain record, using a public block explorer and OpenTimestamps — or the offline verifier we give you. Verification never requires notaros to be online or in business.
Which blockchains does notaros use?
Every full-service proof is anchored to Base and to Bitcoin through OpenTimestamps. Bitcoin gives the strongest long-term permanence; Base gives fast, low-cost confirmation. You get both.
Is a blockchain notarization legally valid?
notaros produces strong, independent evidence that a document existed at a point in time and has not changed since. How that evidence is weighed varies by jurisdiction and use, so treat it as robust proof of existence and integrity, and consult a qualified professional for a specific legal matter. notaros is not identity notarization or Remote Online Notarization (RON).
What does it cost?
Three published, self-service prices — no account, no quote from a human. Full service (web) is $25 per document: both anchors, a signed PDF certificate, and hosted plus offline verifiers. Programmatic anchoring through the API, MCP, A2A, or x402 is $3 per anchor — a signed JSON receipt plus an OpenTimestamps .ots proof, no PDF. Anchoring many documents as one Merkle batch drops the per-document price automatically on a published curve, from $3 down to $0.15 each — computed by /quote, no negotiation. Pay-as-you-go in USDC or USDT, no subscription.
A record that outlives the company that made it.
Seal your first document in under a minute, or read exactly how the proof is built and checked.