Let’s Seal

Prove any file is yours — and hasn't changed

Any file you want to prove you had, unchanged, by a certain date — a manuscript, a design, a contract, a photo. Seal it or timestamp it, and you hold independent, dated evidence anyone can check, free, forever.

For anyone with a file worth proving.

Open the app Developer docs
What a seal proves

Four guarantees, in individuals & freelancers

You had it by a certain date

A timestamp on Bitcoin pins the moment your file existed — the evidence that settles “I had this first” for writing, designs, or ideas.

Unaltered since you sealed it

The file is byte-for-byte as you fixed it. Any later change fails verification, so the dated version is provably the version.

Attributable to you, if you want

Sign in with Google or GitHub to attach your verified email to the seal — attribution by a provider you already use, layered on top of the timestamp.

Free, and provable forever

The Bitcoin anchor doesn't depend on any company. A file you seal today stays verifiable indefinitely, by anyone, with standard tools.

How it works

From your file to a proof anyone can check

The same pipeline every time — the seal and the timestamp travel with the file, so the proof is self-contained.

Your file
Your document or file
Seal
Signed over every byte · PAdES / detached CMS
Anchor
Bitcoin timestamp + public transparency log
Proof page
A permanent /d/… link travels with the file
Anyone verifies
Free, public, offline-capable — for anyone
The proof travels inside the file. Verification stands on the published root, the transparency log, and the Bitcoin ledger — so a court, a bank, or a counterparty can check it independently, forever.
Step by step · the web app

Seal it in the app — no setup

  1. 1

    Sign in — Google or GitHub

    Open app.letsseal.org and sign in with an account you already have. No new account to create.

  2. 2

    Seal or timestamp your file

    Drop in the file. Seal it to attach your verified identity, or just timestamp it to prove existence and date — your choice.

  3. 3

    It's anchored on Bitcoin

    The file's fingerprint is timestamped on Bitcoin and recorded in the public transparency log. You get a proof link and, for files, a normal copy that also verifies.

  4. 4

    Keep the proof

    Save the proof link or the .ots file. It's the independent, dated evidence you produce if anyone ever questions who had the file first.

Step by step · the CLI

Automate it from your terminal or CI

The sealbot CLI does the same thing, scriptably — one command per file, straight into your pipeline.

# Timestamp any file — only its hash leaves your machine
$ sealbot anchor my-manuscript.docx --publish
anchored my-manuscript.docx → my-manuscript.docx.ots
  proof  https://letsseal.org/d/…  (digest only — file never uploaded)

# Prove the date later, against Bitcoin, with stock tooling
$ ots verify my-manuscript.docx.ots
Success! Bitcoin attests existence as of 2026-06-30

# Or verify a file someone sent you is unchanged
$ sealbot verify deliverable.pdf
✓ authentic · unaltered

Anchoring proves existence-and-date without the file ever leaving your machine — only its SHA-256. Sign in with Google or GitHub if you also want your verified identity attached. Both are free.

Full CLI & API reference
See it in action

What a proof looks like, and what you can seal

Issuer verified — controls letsseal.org
Authentic & unaltered
Document
A timestamped manuscript or design
Issuer
Let’s Seal Examplesletsseal.org
SHA-256
64-hex fingerprint ✓

Anchored on Bitcoin

Recorded in the public transparency log

Public and free to verify — by anyone, with standard tools.
Open the live proof

A single use case, many documents. Each of these is sealed the same way:

  • A timestamped manuscript or design

    Live proof

    Open the proof page the way you'd show it to prove you had the work first: it shows the file is unaltered and independently timestamped on Bitcoin — a date no one can move.

  • A freelance deliverable

    Seal what you hand a client so both of you can prove exactly what was delivered, and when — no argument later about which version was sent.

  • A personal agreement

    Seal an agreement between individuals so each party can prove the terms are exactly as agreed, and which version was signed.

  • A private file (hash-only)

    Anchor just a file's SHA-256 — the file never leaves your machine — and still prove you had it, unchanged, by a date. Reveal it only if you choose to.

Live proofs are real documents sealed under the “Let’s Seal Examples” organisation.

Common documents

What you’ll seal

  • Manuscripts & writing
  • Designs & creative work
  • Personal agreements
  • Photos & video
  • Freelance deliverables
  • Important documents
Questions

Straight answers

Do I need to create an account?
No new account — sign in with Google or GitHub to attach your verified identity, or just anchor a file's hash from the CLI with no sign-in at all. Either way it's free.
Is it really free?
Yes. Sealing and timestamping are free, and verifying is always free for anyone — the proof stands on public infrastructure, not on paying us.
How does this prove I created something first?
It pins your file to a Bitcoin timestamp, so you can prove it existed by that date. If someone later claims the work, your dated, tamper-evident proof came first.
Can I keep the file private?
Yes. Anchor just the SHA-256 — the file never leaves your machine, only its 32-byte digest, and the timestamp still proves it existed by that date. You reveal the file only if and when you want to.

Start sealing individuals & freelancers documents

Free and open. Seal in the app, automate from the CLI, and hand anyone a proof they can verify themselves.

Open the app All use cases