For artwork, ideas, videos, documents & AI output
Mark anything to prove it came from you and when you made it.
Mark creates a signed fingerprint showing that your account had this exact version at this moment. Anyone can check it. Your file never leaves your device.
Choose a file
We fingerprint it here, then return a signed record you can share.
Drop a file here, or click to choose
Hashed locally · the file is never uploaded
Add details (optional)
Shown on the record page. Leave blank to say nothing.
Try it right now
Stamp a file. Then try to fool the check.
A live demo of the whole loop, running entirely in your browser. Nothing is uploaded and nothing is saved.
Drop any file here to stamp it
Fingerprinted locally: it never leaves this page
Stamped
Sealed by you, just now
Demo stamp · not saved
your-file.pdf
- Stamped
- now
- Fingerprint
- …
Now check it. Drop the same file to see a match. Or open it, change one character, save, and drop that: watch the check refuse it.
Drop a file to check it
That's the whole product. A real stamp is this, made permanent: sealed to a public record anyone can check, forever.
A copied badge or QR proves nothing on its own. Verification is the file matching the fingerprint, not the sticker. A screenshot or re-save won't match, and that's the point.
The problem
Every AI-era file raises two questions.
A stamp answers both, and lets you keep the answer.
Who really made it?
Anyone can put a name or logo on a file. Real provenance ties it to a publisher who has proven they control that identity: a domain, a handle, an account.
Mark shows a verified publisher (whitehouse.gov, or @you), never a name someone just typed.
Is this the exact thing they made?
One changed word or pixel is a different file. Mark fingerprints the exact bytes, so an edit can't hide behind a familiar look.
Drop the file and Mark confirms it is byte-for-byte the sealed original.
Use Mark wherever you work
The browser, your agent, and your own app all create the same signed, shareable record.
Tell your coding agent to stamp it
Add one line to your MCP config, and your AI agent stamps whatever it writes for you, no copy-pasting hashes. Works in Claude Code, Claude Desktop, Cursor, Windsurf, Tatastu, or any tool that speaks MCP.
claude mcp add --transport http mark https://makemark.io/mcp
Straight from your own code
Hash locally, POST the fingerprint, get a permanent verify URL back. Any language, any pipeline, any agent you're building yourself.
import { createHash } from "node:crypto"
import { readFileSync } from "node:fs"
const bytes = readFileSync("report.pdf")
const hash = createHash("sha256")
.update(bytes)
.digest("hex")
const res = await fetch(
"https://makemark.io/proof",
{
method: "POST",
headers: {
"content-type": "application/json",
authorization: "Bearer pk_your_key",
},
body: JSON.stringify({
contentHash: hash,
title: "Q2 report",
visibility: "public",
}),
},
)
const { verifyUrl } = await res.json()
console.log(verifyUrl)Sign in once for a free key, or let your code pay per stamp automatically and skip the account. Full API docs →
The difference
You own the proof. It outlives us.
Mark signs your fingerprint immediately, then anchors daily batches to Arweave. Base is an optional additional witness, not currently enabled. Once anchored, download a bundle to check the signed receipt and Merkle path with no internet connection. Keep the bundle and original file: verification need not depend on Mark.
- Daily anchoring writes a batch record to Arweave
- Download a bundle that verifies with no internet at all
- Your content never leaves your device, only its fingerprint does
- Checked by an MIT-licensed verifier on npm that runs on your own machine
Identity, free
Prove it's you, no matter who you are
A C2PA signing certificate costs about $289 a year. Ours is free and self-serve: prove a domain or a handle by publishing a token only you can. Or skip it entirely and just get a timestamp you own.
Orgs & newsrooms
Verify your domain with a DNS record, then get a hand-vetted Official badge. For gov, press, and brands.
Creators & influencers
Prove a handle with a GitHub gist or a posted token. Your public page becomes your "everything I post is checkable" link in bio.
A napkin idea
No identity step. Sign in, drop the photo, and own a permanent timestamp that you had this exact thing first.
Made for making things
One small mark. Very different reasons.
Use it whenever the exact file and the moment you had it matter. New to it? See how to timestamp a file, or how to check one you were sent.
The artist's working file
Mark the layered illustration before it leaves your studio. Months later, you still have a checkable record for the exact working file, not just a screenshot.
Useful when process, timing, and the original source file matter.
The founder's napkin idea
Photograph the sketch, mark it, and keep building. The record does not award ownership; it shows that your account had this exact version on this date.
A lightweight habit for ideas that are too early for paperwork.
The creator's original video
Mark the exported original before posting. Put the public check link in your bio so followers can distinguish your signed file from a repost, edit, or impersonator.
A verified handle answers “did this exact file come from that account?”
The research snapshot
Mark a dataset, notebook, or model output before sharing it. Collaborators can check which exact snapshot your result refers to.
A durable version reference that survives renamed files and forwarded links.
The musician's first demo
Mark the bounce before sending it to a collaborator, label, or client. The private audio stays on your machine; the signed fingerprint and time become the record.
The useful evidence is the exact mix and the moment, not another cloud upload.
The agent's finished work
Give your AI one standing instruction: mark every final artifact. It can hash locally, use its own API key, and attach the check link wherever the work goes.
Machine-made work gets a machine-checkable chain back to the account that published it.
Agent-native
Your AI agent stamps everything, by itself.
One standing instruction: "stamp everything I publish." The agent gets its own key with one call, no signup page, hashes locally, calls the tool, pays per stamp from its own wallet when needed, and drops the verify link into the post. No forms, no checkout, and every error tells it what to do next.
Read the agent docs- 0 accountcreate_account, no human needed
- 1 hashSHA-256, locally
- 2 stampcreate_proof over MCP or REST
- 3 payx402 USDC, autonomous
- 4 attachverifyUrl + badge + QR
- 5 recoverevery error says what's next
AI transparency · Article 50(2)
A provenance layer for AI output
Mark can support your disclosure workflow with a machine-readable record for an exact file. It does not by itself detect AI content, survive changes to the file, or guarantee EU AI Act compliance. Keep the original bytes and pair the record with appropriate labels and legal guidance.
Questions
Straight answers
What a stamp does, what it honestly does not, and how the durable parts work.
Is a Mark legally valid?
A Mark is strong, tamper-evident evidence, not a court ruling. It shows that a specific file existed in a specific state at a specific time, sealed under a signature and written to public records anyone can re-check. Timestamped evidence like this is weighed by courts and platforms every day. What it does not do, on its own, is decide who owns a work or who is telling the truth.
Do you upload or store my file?
No. Your file is fingerprinted on your own device, and only the fingerprint (a short code that cannot be turned back into your content) is sent. The file itself, your photo, document, or draft, never leaves your browser or your machine.
What happens if Mark shuts down?
Download your verification bundle after anchoring. Its signed receipt and Merkle path can be checked offline even if Mark shuts down. Daily batches anchor to Arweave; Base is an optional additional witness, not currently enabled. Checking the public anchor independently requires access to that ledger.
How is this different from a notary or a copyright registration?
A legal notary confirms identity and witnesses a formal act. Mark does something narrower: it records that an account signed this exact file at this moment. It is instant and machine-checkable, but it is not a legal notarization or a copyright registration.
What does it cost?
Verifying anything is free forever, with no account. Every durable Mark account gets one lifetime sample stamp. Prepaid packs never expire: 5 for $1.00, 10 for $1.50, 50 for $5.00, 100 for $8.00, 500 for $35.00, 1,000 for $65.00, 2,000 for $120.00. Signing in with your email adds 100 included stamps a month, and agents can also pay per stamp with x402.
Can an AI agent use this without a human?
Yes. An agent can create its own key, fingerprint a file, stamp it, and attach the verify link entirely on its own, with no signup page and no person in the loop. Every error message is written to tell the agent exactly what to do next.
Does a stamp prove I am the original author?
It proves possession at a time, not authorship truth. A stamp shows you held this exact file on this date, which is decisive when timing or who-had-it-first is the question. It cannot know whether you created the content or copied it, so treat it as a timestamp you own, not a verdict on originality.
Want the longer version? Read about what a timestamp really proves, or how it compares to other timestamping services.