# Compare timestamping services. Pay per call, or subscribe?

Eight ways to prove a file existed, side by side: what each costs, whether you need an account, how many files you can send at once, which blockchain it anchors to, and what you get back. Every vendor’s own page is linked, so you can check us.

## The short answer

- **One file, once, and you want free:** [OpenTimestamps.org](https://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](https://x402.org), 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](https://stampthisfile.com/evidence).

## 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.

| Service | Pay model | Price | Account or API key | Batch | Proof you get |
| --- | --- | --- | --- | --- | --- |
| stampthisfile | Pay per call, USDC | $0.05 per hash | None | 1–100 hashes per request | .ots (OpenTimestamps) |
| OpenTimestamps.org | Free | $0 | None | One file at a time in the browser | .ots (OpenTimestamps) |
| OriginStamp | Subscription, quoted | Quote; 2020 list started at $9.90/mo for 100 | Yes, API key | API, batched internally | Vendor proof and certificate |
| Woleet | Subscription | From €49/mo (1,000 stamps) | Yes, contract | API, high rate limits | Vendor proof, Bitcoin-anchored |
| Simple Proof | Subscription and top-ups | Free 5; $10/mo for 10; $30/mo for 30; extra $0.75–$1.00 each | Yes, keys by email | API, per file | Vendor blockstamp |
| Chainpoint | Free software | Node and hosting costs | No, for your own node | Per node | Chainpoint JSON proof |
| Stampery | Subscription, quoted | Quote | Yes, dashboard and API key | API, enterprise certification | Vendor certificate, blockchain-recorded |
| Germain Maureau | Service, quoted (IP firm) | Quote | Yes, dashboard | One file at a time in the dashboard | PDF certificate, anchored on Tezos |

_Read off each vendor’s own site in October 2026: [originstamp.com](https://originstamp.com), [woleet.io/pricing](https://www.woleet.io/pricing/), [simpleproof.com/pricing](https://www.simpleproof.com/pricing), [opentimestamps.org](https://opentimestamps.org), [chainpoint.org](https://chainpoint.org), [stampery.com](https://stampery.com), [germainmaureau.com](https://germainmaureau.com/en/solution/blockchain-timestamping), 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](https://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](https://stampthisfile.com/evidence).

## Head to head

Two comparisons go deeper, because they are the decisions we see most: [stampthisfile vs OriginStamp](https://stampthisfile.com/compare/originstamp), the subscription incumbent, and [stampthisfile vs OpenTimestamps.org](https://stampthisfile.com/compare/opentimestamps), the free tool on the same protocol. For prices at your volume, including a worked cost table, see [pricing](https://stampthisfile.com/compare/pricing).

## Also worth knowing

- **ProofLedger** ([proofledger.io](https://proofledger.io)) anchors file hashes to blockchains for proof of existence, with an account model.
- **SafeStamper** ([safestamper.com](https://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](https://evercert.io)) is a free browser tool for blockchain-anchored document timestamps, similar in shape to the OpenTimestamps.org page.
- **DGI** ([dgi.io](https://www.dgi.io/ots)) 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

### Which of these is cheapest?

For small volumes, the free tools: OpenTimestamps.org costs nothing. Among paid services, a per-hash price ($0.05 here) is cheapest for most volumes, because subscriptions price in a dashboard, support and an allowance you may not use: at 100 files a month that is $5.00 here against about $83 on Simple Proof’s best public rate and €49 at Woleet. At 1,000 files it is within a few dollars of Woleet’s €49 allowance, and above that an enterprise quote is the conversation. See [pricing](https://stampthisfile.com/compare/pricing).

### Which one is fastest?

They share the same limit: a Bitcoin block. A proof is pending until a block confirms it, usually within 1–6 hours on the public calendars. What differs is what you get before then. We return a valid pending `.ots` immediately, upgrade it when the calendars commit it (including inside `/v1/verify`), and send a webhook on completion.

### Do all of these anchor in Bitcoin?

Bitcoin is the common anchor, not the only one: OpenTimestamps calendars commit to Bitcoin, and OriginStamp’s documentation describes more than one blockchain. A proof is only as useful as the chain you can independently check, and Bitcoin block headers are the easiest to check for free.

### Can I verify a proof without the vendor?

With an `.ots` proof, yes: upload the file and proof at [opentimestamps.org](https://opentimestamps.org), or run `ots verify` against your own Bitcoin node. Vendor-format proofs and PDF certificates usually need the vendor or their API — lock-in by format, not by contract. If independence matters, ask for the export format before you buy, and whether a third party can check it without an account.

### Which services work best for AI agents, and which for humans?

Agents need an endpoint they can pay for and read: machine-payable (x402 here), no key a human has to provision, a batch call and a completion callback. Humans stamping a document now and then need none of that, and should use the free [opentimestamps.org](https://opentimestamps.org) page. Compliance and legal teams need a dashboard, certificates and an invoice, which is what the subscription services sell. The [agent guide](https://stampthisfile.com/guides/agents) has the loop in code.

_Checked October 2026. HTML: https://stampthisfile.com/compare · Agent docs: https://stampthisfile.com/llms.txt_