Compare timestamping services.
Pay per call, or subscribe?

The short answer

• One file, once, and you want free: OpenTimestamps.org. It is the same standard we use, in a browser, with no account.
• Software stamps on its own, in volume: stampthisfile. $0.05 per hash in USDC through x402, no account or API key, up to 100 hashes per request, and a webhook when Bitcoin confirms them.
• Procurement wants an invoice, a dashboard and someone to call: OriginStamp, Woleet or Simple Proof. All three are subscriptions with a named vendor behind them.
• You need a legal presumption of the date (eIDAS qualified timestamp): none of the services here. That needs a provider on the EU trusted list. See what a stamp proves.

Side by side

The four things that actually change the decision: who pays, what you commit to, how much you can send at once, and what you can hand to someone else.

Read off each vendor’s own site in October 2026: originstamp.com, woleet.io/pricing, simpleproof.com/pricing, opentimestamps.org, chainpoint.org, stampery.com, germainmaureau.com, and this site. Where a vendor does not publish prices, the cell says “Quote” rather than a guess. Plans change; check before you budget.

What actually differs

Every service here does the same core thing: it takes a SHA-256 hash, mixes it into a Merkle tree, and commits that tree to a blockchain. A timestamp that says “this hash existed before block N” is the product. The differences are all in how you buy it and what you get back.

• Access model. Free and open (OpenTimestamps.org, Chainpoint), pay-per-call (us), or subscription with an account (OriginStamp, Woleet, Simple Proof). Subscriptions exist because most buyers want an invoice, a contract and a support address.
• Unit of sale. A hash, a file, or a month. Ours is the hash: three hashes in one request cost three times the unit price, and the payment settles once. Subscriptions sell you an allowance and charge for overage.
• Batching. Up to 100 hashes per request here, in one payment and one signed receipt. The free browser tool takes one file at a time. Subscription APIs batch too, and each file still counts against your allowance.
• What you get back. An .ots file is the OpenTimestamps standard: any OTS tool, including opentimestamps.org and the ots client, verifies it without us. Vendor proofs and certificates verify through the vendor or their API. That is the difference between a proof you keep and a proof you rent.
• When it completes. Nothing anchored in Bitcoin is final on arrival. You get a pending proof immediately, and it becomes complete when a Bitcoin block confirms it, usually in 1–6 hours. “Instant” in a vendor’s copy usually means the receipt is instant, not the anchor.

How the Bitcoin anchoring works

The same four moves, whichever service you pick. The differences start in what you are handed at the end.

1. You send a fingerprint, never the file. SHA-256 of the bytes; the file stays where it is.
2. It joins a tree. Here it is mixed with a random 16-byte nonce, so it cannot be recognised, then combined with other hashes into a Merkle tree. The root is the only thing that goes on chain.
3. A calendar commits the root. We submit it to four independent public OpenTimestamps calendars; each folds many customers’ roots into one Bitcoin transaction. At least two must accept, or nothing is charged.
4. The block fixes the time. When the transaction confirms, the calendar returns the path from your hash to the block header. That path is your .ots proof, and the block’s timestamp is the claim: these bytes existed no later than then.

Anyone can replay that path: hash the file, walk the proof to the block header, compare the header with Bitcoin. That is why the proof does not need us, and why a proof in a vendor’s own format does. Providers that anchor to other chains (Germain Maureau uses Tezos, OriginStamp describes more than one blockchain) are doing the same trick in a different ledger; the question to ask is who can check the result without them.

How to choose

In this order. The first two questions decide most of it.

1. Who pays? A person with a card can use any of these. Software with a wallet needs a machine-payable endpoint: x402 here, or an API key a human provisions in advance.
2. What volume, and does it spike? Ten files a month fits a $10 plan. Ten thousand in an afternoon does not, and a per-call price does not care.
3. Do you need a batch and a callback? A pipeline that stamps every model output wants one call for many hashes and a notification when the proofs complete, not a browser tab per file.
4. Must the proof outlive the vendor? If yes, insist on OpenTimestamps .ots proofs, or on a vendor that commits to exporting them.
5. Is a timestamp all you need? If you also need to prove who made the file, you need a signature. If you need the date to carry a legal presumption, you need a qualified timestamp. A stamp is neither. See Evidence.

Head to head

Two comparisons go deeper, because they are the decisions we see most: stampthisfile vs OriginStamp, the subscription incumbent, and stampthisfile vs OpenTimestamps.org, the free tool on the same protocol. For prices at your volume, including a worked cost table, see pricing.

Also worth knowing

• ProofLedger (proofledger.io) anchors file hashes to blockchains for proof of existence, with an account model.
• SafeStamper (safestamper.com) leans towards legal evidence: it generates technological and legal evidence that a file existed at a date, with an account.
• EverCert (evercert.io) is a free browser tool for blockchain-anchored document timestamps, similar in shape to the OpenTimestamps.org page.
• DGI (dgi.io) has an OpenTimestamps page aimed at developers, alongside a broader records platform.
• We have not tested these four, and their entries are shorter for that reason. They appear because they are alternatives you will find, not because we recommend them.

Questions