ProofLedger Reproducible math, not blind trust.

Browser-side SHA-256 · Anchored in Bitcoin · No trusted third party

Anchor what you know, before they say you didn’t.

Drop a file or paste text. Your browser computes its fingerprint locally and stamps the fingerprint into the Bitcoin blockchain via OpenTimestamps. The original content never leaves your device. What you get back is a permanent, reproducible receipt.

Your file stays local Only the hash is recorded Verifiable by anyone, forever

01

Certify

Make a proof.

The fingerprint is computed in your browser using the Web Crypto API. The original bytes are never uploaded.

SHA-256 fingerprint Waiting for input

02

How it works

Four steps. No magic.

  1. 01

    Prepare a stable document.

    PDF is ideal because the bytes don’t shuffle. Any file works — the fingerprint is computed over raw bytes, not over the rendered content.

  2. 02

    Compute the fingerprint locally.

    Your browser hashes the file with SHA-256 via Web Crypto. The hash is the only thing sent to ProofLedger. We never see the file’s bytes, name, or text content.

  3. 03

    Anchor the fingerprint in Bitcoin.

    We submit the hash to the OpenTimestamps calendar network, which aggregates it into a Merkle tree and anchors the root in a Bitcoin block. Roughly six hours later, your proof carries a real block height.

  4. 04

    Keep the proof. Keep the original.

    Verification needs both. Anyone with the original file plus the proof can recompute the hash and confirm the Bitcoin attestation independently — no ProofLedger required.

03

Verify

Match the original to a proof.

Pick a proof you’ve created in this browser, then re-supply the original file or text. Verification recomputes the fingerprint client-side and compares.

Against your registry

Create or select a proof first.

Without ProofLedger

You don’t need this site to verify a proof. Anyone holding the original file plus the evidence bundle can do it themselves:

  1. sha256sum yourfile.pdf → recompute the hash on your own machine.
  2. ots verify opentimestamps.ots → confirm the Bitcoin attestation against a Bitcoin node.
  3. Compare your computed hash to the value in proof.json. If they match and OTS confirms, the proof is valid.

04

Registry

Your proofs in this browser.

Write tokens are kept in localStorage on this device only. Lose this browser, lose the ability to upgrade — keep the evidence bundle as your portable copy.

05

Transparency

What ProofLedger sees. What it doesn’t.

What we see

  • The 64-character SHA-256 hash you submit.
  • The title and (if you submitted one) the file name.
  • An optional private note. Never shown publicly.
  • The OpenTimestamps proof bytes returned by the calendar.
  • Your IP, briefly, for rate-limit accounting.

What we don’t see

  • The file’s bytes, contents, or text body.
  • Any password, key, or identifier inside the file.
  • Other documents that share the same fingerprint (there are none).
  • Whether the same file has been certified elsewhere.
  • Anything about who you are, unless you tell us.

06

Use cases

A short, opinionated list of what to certify.

Anywhere a date matters more than a signature. Examples are fictional but the format is real.

Ideas

“Pitch deck v1 — Skylark”

f4a91b3e…d27c

Anchored · 04 / 03 / 2026

Predictions

“Election call — district 4”

9b031c…77a8

Anchored · 11 / 05 / 2026

Research

“Hypothesis register — batch 17”

2c11e9…1f4d

Anchored · 22 / 02 / 2026

Legal

“Whistleblower memo — pre-disclosure”

cc88d3…02b9

Anchored · 09 / 01 / 2026

Art

“Lyrics — track 03”

7a3e21…4b10

Anchored · 30 / 03 / 2026

Real estate

“Move-in inventory — apt 4B”

d50fa1…9930

Anchored · 18 / 04 / 2026

Personal

“Promise letter — sent unsigned”

10ef99…aa01

Anchored · 05 / 02 / 2026

Digital

“Post text before deletion”

5b22d4…ce72

Anchored · 27 / 03 / 2026

Yours

Whatever a date will matter for, later.

Add it to the registry above ↑