The local-first way to prove what you and an AI actually said.
witness turns a ChatGPT, Claude or Gemini conversation into a tamper-evident record — signed on your device, never uploaded, and independently verifiable by whoever you send it to.
Screenshots can be faked. A witness record can't.
What a Witness Record Gives You
The conversation, exactly as it happened
You start a recording when it matters. Each turn is captured on the page and written into an append-only chain, so the order of what was said is fixed at the moment it was said.
- User-initiated — nothing is recorded until you say so
- Every turn hash-chained to the one before it
- Selector profiles versioned per site
Signed on your device, with a key you hold
Each record is signed locally with ECDSA. Only a digest ever touches the signing path — the text of your conversation is never part of a network request.
- Per-record ECDSA signature
- Keys generated and held on your machine
- Digest-only signing, even on the hardware tier
Anyone can check it without trusting you
Export a sealed Witness Record and the recipient re-runs the same checks you did, on an independent verifier. Reproducibility, not reassurance.
- A signed export manifest fingerprints every file
- Verification is free, forever
- One verifier for machine and human evidence
Three Steps, Start to Proof
From an ordinary chat to a record a stranger can check — without your conversation ever leaving the machine.
Start the record where the conversation happens
Open witness on ChatGPT, Claude or Gemini and press Start Recording. From that moment every turn is hash-chained and signed on your device — nothing is captured before you ask for it.
Take the evidence package with you
Stop recording and witness writes a single .zip: the conversation, the hash chain, the signatures, and the certificate that ties them to your key. It lands in your downloads folder, not on a server.
Let anyone check it independently
Whoever receives the package drops it into the open verifier. The chain is recomputed link by link, every signature is checked, and the certificate is walked back to a trusted authority — no account, no access to you.
Move the signing key off the machine entirely
On the hardware-rooted tier the signing key lives on a physical token. Unplug it and no new record can be signed — and even then, only a digest ever reaches the key.
Privacy Is the Architecture, Not the Policy
Most AI chat loggers work by uploading your conversations to their servers. witness inverts that: capture on the page, sign locally, upload nothing.
Content stays local
Conversation text, page snapshot and record chain live in your browser profile. There is no witness server holding your chats.
What actually crosses the wire
Only identity endpoints — email confirmation, a code, a certificate request, a thumbprint. Never conversation content.
Local, digest-only signing
The signing path sees a SHA-256 digest, not your text. That holds for software identity and hardware identity alike.
After you export, it's yours
A Witness Record is a file. Once you share it, distribution is in your hands — we can't recall it, and we can't read it.
Your conversation content never leaves your device unless you choose to export and share it.
Works Where You Already Work
witness runs on a narrow, explicit allowlist of three sites — not on every page you visit.
- ChatGPT — chatgpt.com
- Claude — claude.ai
- Gemini — gemini.google.com
Site access is scoped to exactly these three domains. When an assistant redesigns its interface the selector profile is updated and versioned, so older records stay auditable.
What It Proves — and What It Doesn't
What was said, in what order, unaltered
The hash chain is the strong claim. Change one character in an exported record and verification fails — and tells you where it broke.
Who said it — on the Verified tier
Free identity proves integrity while the signer stays anonymous. Verified binds an email-checked identity into every record. Free proves nothing was changed; paid proves it was you.
When — is a device clock
Timestamps come from the signing machine's own clock, not an independent timestamp authority. Every verification result says so. witness is designed for chain-of-custody; we do not claim legal admissibility.
Powered by AuthentAI — the same evidence engine built for industrial machine insurability.
Make Your First Witness Record
Step one is a Chrome install and takes about a minute. The free tier is the whole product — no account, no hardware, nothing uploaded.