ByHand

About

Prove your email was written by you — not by an AI.

ByHand is a Chrome extension for Gmail that quietly analyzes
the rhythm of your typing as you compose a message — when you
pause, how often you go back and edit, the cadence between your
sentences — and stamps your outgoing email with a verifiable
signal that a real person wrote it. Recipients click the stamp
to view a short report explaining the basis for the score. Nothing
about the *content* of your email ever leaves your computer.

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WHAT BYHAND DOES
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When you write an email in Gmail, ByHand watches HOW you type,
not WHAT you type. From the timing of your keystrokes alone, it
computes an authorship score on a 0–100 scale. If the score is
high enough, ByHand attaches a small footer stamp to your email.
Recipients who click the stamp see a clean web page with the
score, a one-sentence summary ("Written by a human in 2 sittings
over 8 minutes"), and an expandable view of the timing patterns
that led to it.

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WHY INSTALL IT
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• Vouch for your own writing. When you've put real thought into
  an email, recipients can see it was actually you typing — at
  your own pace, in your own words.

• Let recipients verify. No more guessing whether that thoughtful
  email was drafted by a chatbot. The stamp gives the recipient
  something concrete to inspect.

• Privacy-respecting by design. ByHand never reads or transmits
  the text of your email. Only timing statistics — pause
  durations, keystroke variance, edit counts — leave your device.

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KEY FEATURES
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• Live, passive analysis. No interruption to your flow.
• Two footer stamp styles: with hand icon, or text-only.
• Optional subject-line tag (green-square emoji, "Written By Hand,"
  or your own custom prefix).
• One-click verification: recipients see a public report page at
  a random 8-character URL.
• Per-email, not per-account. Every email gets its own report.
  Unsigned emails carry no stamp.
• Minimal permissions: storage, activeTab, tabs — host access only
  to mail.google.com and your Supabase backend.

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HOW IT WORKS
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While you type, ByHand records the moment each key is pressed
and released — never which key it was. From those timestamps it
derives statistics like:

• How long you pause before starting each sentence (humans pause
  to think; pasted text doesn't)
• How variable your typing rhythm is (humans are bursty; AI-pasted
  text is uniform)
• How many corrections you make
• Whether you pasted any chunks of text

These statistics feed into a research-backed scoring model. The
output is one number from 0 to 100, mapped to three verdicts:

• 65–100 — BYHAND. Clear evidence the text was typed live.
• 45–64  — MIXED / ASSISTED. Some passages may have been pasted
           or composed elsewhere.
• 0–44   — AI GENERATED. Strong evidence the text was not typed.

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WHAT BYHAND NEVER DOES
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✗ Reads the body, subject line, or any text of an email
✗ Captures which keys you press (only when, not what)
✗ Sends data to any advertising network
✗ Tracks browsing outside Gmail
✗ Trains AI models on your data
✗ Sells, rents, or shares your information

Full privacy policy: handstencil.com/privacy

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WHAT RECIPIENTS SEE
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Recipients do not need ByHand installed. They see the stamp at
the bottom of your email. Clicking it opens a web page showing
the score, verdict, and timing summary. The page never displays
the content of your email — only the rhythm statistics.

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LIMITATIONS WORTH KNOWING
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• ByHand watches typing, so it can't certify text you pasted from
  your phone, drafted in another tool, or transcribed from voice.
  Those will read as Mixed or AI Generated even if you wrote them.
• Very short messages don't carry enough signal to score reliably.
• ByHand currently operates only in Gmail (mail.google.com).
  Google Docs and other platforms are on the roadmap.

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WHO IT'S FOR
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• Journalists, researchers, and lawyers who need to vouch for
  the authorship of correspondence
• Founders and consultants who still write personal emails and
  want recipients to know it
• Anyone who wants to push back on the assumption that every
  long-form email is now AI-generated

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GET STARTED
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Install ByHand, pin the toolbar icon, flip the master toggle on,
and write an email in Gmail. The stamp appears automatically when
your score qualifies. That's it.

ByHand is a product of Hand Stencil. Learn more at handstencil.com.