What does it cost
to timestamp a file?

How much does stampthisfile cost?

It costs $0.05 per hash, paid in USDC on Base, with no account, no subscription, no minimum and no API key. A batch of 100 hashes costs 100 × $0.05 and settles in a single payment. Payment is through x402: the payer signs an EIP-3009 authorization, the facilitator pays the gas, and nothing else is charged.

The price is in the 402 answer, not in a contract. Send POST /v1/stamps without a payment and the response body and the PAYMENT-REQUIRED header carry the exact amount for that request, so a batch of 7 hashes is quoted as 7 × the unit price before anything is signed.

Pay-per-use vs subscription, in numbers

Monthly cost for a given number of files, at list prices. Subscription figures assume you buy the cheapest plan that covers the volume, with overage at the vendor’s published top-up rate.

Woleet’s pricing page mentions an annual commitment around its enterprise tier, while its FAQ says plans can be monthly or annual; check before you budget. Simple Proof’s overage is $1.00 per extra blockstamp on Personal and $0.75 on Business, sold in packs. OriginStamp quotes per customer today; its 2020 price list is the last public one. Stampery and Germain Maureau also quote rather than publish, and Germain Maureau anchors on Tezos rather than Bitcoin. Links to every vendor are on the comparison page.

A subscription buys an allowance you may not use, plus a dashboard, invoices, support and, at the top end, an SLA. The effective rate on the plans above runs from $1.00 (Simple Proof Personal) to €0.049 (Woleet’s 1,000-stamp plan) per file; here it is $0.05. The per-hash price wins clearly at small and medium volumes, and at around 1,000 files it is within a few dollars of Woleet’s allowance — the point where a dashboard and a monthly invoice start to be worth the difference. Above that, enterprise pricing is a conversation, not a rate card.

So the honest break-even is not a volume. It is a feature: the moment you need a purchase order, an invoice with a VAT number, a named support contact or a dashboard your legal team can open, a subscription is worth its premium, and you should buy one.

Do I need an account or API key?

Not here. There is no signup, no key to rotate and nothing to leak. The wallet that signs the payment is the credential: the receipt names the payer address, and a retry with the same payment and the same body returns the same proofs without paying twice.

OriginStamp, Woleet and Simple Proof all issue credentials: an API key, a contract, or keys emailed after sign-up. That is fine for a team, and awkward for an agent that has to be handed a secret. If a human has to create the key, the human is in the loop, and the key is a thing that can end up in a log.

One thing an account does buy: someone to invoice. If that matters, buy the account. Paying per call here means paying from a wallet your finance team has to fund with USDC, which some organisations will not do.

How many hashes can I batch in one call?

Up to 100 per request, all at the unit price, in one payment and one Merkle root. Each hash gets its own proof file and its own status URL, so a batch is just a cheaper, faster way to stamp many files, not a different product. A repeated hash in the same request is rejected with a 400 rather than silently deduplicated, so you notice a bug in your manifest.

Batching is also where the fixed costs go away. A single USDC settlement covers the whole batch, which is why 100 hashes cost 100 × $0.05 and not more. Subscription services batch internally for the same reason: one on-chain commitment can carry thousands of hashes.

How long until a Bitcoin-anchored timestamp is confirmed?

Immediately, you get a valid pending proof. It names the calendars that will commit your hash to Bitcoin, and it already verifies as a proof with no Bitcoin attestation yet. It becomes complete when a Bitcoin block confirms the calendars’ transaction: usually 1–6 hours, occasionally longer if fees spike.

Two things follow. First, do not treat “pending” as done: a pending proof still depends on the calendars, and it is the complete one that stands alone. Download it again later, or let the webhook tell you. Second, POST /v1/verify will finish a pending proof for you: if the calendars have committed it since you stamped, the answer comes back complete with the upgraded .ots attached, which saves you a second integration.

The timestamp itself is the block’s time, accurate to about two hours. A stamp says the file existed no later than that block, never “at exactly” that moment. If you need a time to the minute with a legal presumption, that is a qualified timestamp from a QTSP, not any of these services. What a stamp proves covers the difference.

What the money does not buy

• It is not a signature: it does not show who made the file or that they agreed to it. Sign first, then stamp.
• It is not an eIDAS qualified timestamp: no legal presumption of the date. Admissible in many places, weighed by a judge, as the case law shows.
• It is not a notary and not a certificate about the content: nobody checks that the file is true, only that these bytes existed by then.
• It is not confidential about the payment: the paying address is public on chain, linked to the time of the stamp, not to your hash. Files never leave your machine; only hashes are sent.

Questions