A blockchain timestamp puts your file's fingerprint (a SHA-256 hash of its exact bytes) into a public ledger that nobody, including the service that wrote it, can rewrite or backdate. From then on, anyone can confirm the file existed before that entry. It's the strongest general-purpose "this existed on this date" evidence available to an ordinary person, and in 2026 you can get it for free.
The options differ less in cryptographic strength than in friction, identity, and durability. This comparison is honest about all four tools, including ours; each one is the right choice for somebody.
What to actually compare
- Cost. Free, subscription, or per document.
- Effort. A browser drop versus a command line versus an appointment.
- Identity. Does the record say who, or only when?
- Durability. If the provider vanishes, does your proof still verify?
- The verification story. How hard is it for a third party, a client, an editor, a court expert, to check your claim?
The options
OpenTimestamps
An open protocol, free to use, that anchors fingerprints to the Bitcoin blockchain
through public calendar servers. It's well designed and widely respected: there's no
company to trust, no fee, and the resulting .ots proof file verifies
against Bitcoin on its own, forever.
The trade-off is friction. You'll use a command-line tool or client software, keep the
.ots file safe alongside your document, and wait for a Bitcoin
confirmation before the proof is complete. There's no identity layer (the record says
when, never who) and no hosted page to hand a non-technical person; whoever verifies
your proof needs tooling too. Best for: technical users, archivists,
and anyone who wants zero dependence on any company.
OriginStamp
A commercial timestamping service that grew out of academic research. It anchors document hashes to public blockchains, issues timestamp certificates, and offers an API and dashboards aimed at businesses and compliance workflows. You get a vendor, an invoice, and support, which is exactly what some organizations need.
The trade-off is that it's a paid product, and your workflow runs through a commercial platform. Best for: companies that want timestamping as a supported, invoiced service with certificates to file.
A traditional notary
A licensed human verifies your identity and witnesses the act. That's a genuinely different service from a cryptographic timestamp: it binds a person to a signature with legal formality that courts have recognized for centuries. Some documents (affidavits, deeds, certain contracts) explicitly require it.
But a notary attests to what they saw, not to the exact bytes of a digital file, and each document costs a fee and an appointment. Best for: when a legal process names notarization as a requirement. Not a practical tool for everyday digital work, and not designed to be.
Mark
A browser drop zone: drop a file, get a permanent public record in about 30 seconds. The fingerprint is computed locally (the file is never uploaded), signed immediately with Ed25519, and queued for daily anchoring to Arweave, with Base available as an optional additional witness. The signed receipt is instant; the public anchor follows the daily batch. The record page distinguishes the claimed signing time from the independent anchor time.
Beyond the timestamp, there's an optional identity layer (a free Verified badge for a proven domain or handle, and a vetted Official tier for organizations), C2PA compatibility, and an agent lane: an API and MCP endpoint so AI agents can stamp their own output, with pay-per-stamp via x402. Each durable account gets one lifetime sample stamp, no card; verification is free forever. Honest caveats: it's the newest tool on this list, and like every hash-based method it proves possession at a moment, not authorship truth. Best for: anyone who wants strong timestamping without a terminal, plus identity and a verify link you can hand to anybody.
| Option | Cost | Effort | Identity | If the provider disappears |
|---|---|---|---|---|
| OpenTimestamps | Free | CLI or client app, keep a .ots file | None (time only) | Proof file still verifies against Bitcoin |
| OriginStamp | Commercial plans | Web app or API | Account-based | Certificates reference public blockchains |
| Notary | Fee per document | An appointment | Strong, human-verified | Paper record remains |
| Mark | First stamp free; packs from $1 | Drop a file in the browser | Optional, layered, free | Offline signature + Merkle checks; public anchor checked separately |
Which one should you pick?
If you're technical and want maximum independence from any company, use OpenTimestamps; it's excellent, and free means free. If your organization needs an invoiced vendor with certificates for the compliance binder, look at OriginStamp. If a legal process requires a notary, book the notary; nothing digital substitutes for a legal formality.
If you want the 30-second version, with a link anyone can check, identity you can prove for free, and a record designed to outlive the service, that's what Mark is for. Start with how to timestamp a file for free, and if you're protecting creative work specifically, read how to prove you made something first. Whatever you pick, the advice is the same: stamp early, keep your files, and make sure the proof doesn't depend on any one company staying in business.
Common questions
Is a blockchain timestamp legally recognized?
It's evidence, and how much weight it carries varies by jurisdiction and case. Courts generally treat cryptographic timestamps as supporting evidence of when a file existed, not as a registration or a verdict. This is not legal advice; for a specific matter, ask a lawyer.
Which option is actually free?
OpenTimestamps is entirely free but expects you to run client software and keep a proof file. Mark gives each durable account one lifetime sample stamp, and prepaid packs start at $1. OriginStamp is a commercial service, and notaries charge per document.
Do I need to buy cryptocurrency?
No. Every service compared here covers the blockchain costs itself. Mark is adding an optional pay-per-stamp lane for AI agents (x402, USDC), but humans never need a wallet.
What happens to my timestamp if the service shuts down?
It depends on the design. An OpenTimestamps proof file keeps verifying against Bitcoin on its own. A Mark is anchored to Arweave (Base anchoring is optional), and its downloadable bundle verifies offline with an MIT-licensed verifier on npm. Choose an option where the proof outlives the provider.