Double Check

A second pair of eyes for numbers that can’t be wrong — catch typos and “bank details changed” fraud. Nothing leaves your device.

A second pair of eyes for numbers that can't be wrong. Prevent expensive, embarrassing, and hard-to-reverse mistakes at the exact moment they happen. One transposed digit in a wire transfer sends money to the wrong account — and a fake "our bank details have changed" email sends it to a fraudster. Double Check guards against both. It turns the careful-but-manual ritual — read it, re-read it, ask a colleague to look over your shoulder — into a fast, verifiable workflow right in the field you're typing into, and it remembers each payee's usual account so a switched one stands out. The values you check never leave your computer. HOW IT WORKS Click into the field and press the keyboard shortcut (or right-click → "Double-check this field"). Double Check detects the format, verifies the math, and has you re-type the value from your source document — two independent readings must agree before you attest. Green means match. Red shows exactly what's wrong: "characters 5 and 6 appear swapped" — because transposed digits are the classic transcription error, and naming the mistake beats just flagging it. REAL VALIDATION, NOT JUST PATTERNS • 23 built-in formats: US routing numbers (ABA), IBAN, payment cards, SSN, EIN, SWIFT/BIC, UK sort codes, CLABE, CUSIP, ISIN, VIN, Bitcoin and Ethereum addresses, phone numbers, email, dates, and currency amounts • Formats with check digits are verified mathematically — a single wrong digit in a routing number, IBAN, or card number is caught instantly, often before you re-type anything • Trusted accounts: name a payee once and Double Check warns when an account doesn't match the one you saved for them — the check that catches fake "our bank details changed" (BEC) fraud, which no checksum can. Stores a one-way fingerprint, never the value. • Currency amounts parse US and European separators, refuse genuinely ambiguous ones ("1,234" could be two different numbers — Double Check won't guess), and confirm in words: 1,200,000.00 — one million two hundred thousand and 00/100 • Names the destination country for IBANs and SWIFT/BIC codes, so a payment headed somewhere unexpected stands out • Flags invisible and look-alike characters — a Cyrillic "а" or a zero-width space pasted from a document — that pass a glance but break the value or hide an attack MORE WAYS TO VERIFY • Compare against an image: paste a screenshot or phone photo of the value — read by a bundled OCR engine on your device, never uploaded • Speak it: read the value aloud from the paper in your hand; Chrome's on-device speech recognition transcribes it (Chrome 139+), and nothing leaves your machine • Hear it read back digit by digit by a local on-device voice, at the speed you choose • Empty fields get safe two-step entry: type the value, then re-type it blind — only a matching pair is written into the field PROOF IT HAPPENED • Every attested check is logged: when, where, which field, what format, which methods, and your attestation — never the value itself • Two signatures for the highest-stakes fields: require two people to sign a given field; both names are recorded with the check • Add an optional note to any check — where a value came from, how it was calculated (keep the value itself out of it; it is never stored) • Tamper-evident seal: every entry is sealed with a keyed hash chained to the previous one, and a Verify-integrity button flags any later edit, removal, or reordering — integrity on this device, not identity or legal proof • A "Double-Checked" badge marks the verified field, and flips to a warning if the value changes afterwards • Export the log to CSV or JSON for your records; retention is yours to set MADE FOR REAL WORK • Find the risky fields for you: right-click a page and Double Check tags the high-value fields (account/routing numbers, amounts, IDs) so you know what to verify — it reads field labels, never values • Audit a whole page in one click: right-click → "Check this page for problems" flags every filled field with a real issue — failed checksum, wrong country code, hidden or look-alike character — each with a clearable note • Remembers the right format for each field on each site — the second use is zero-configuration • Define your own formats (vendor IDs, policy numbers, internal account schemes) with clean-up rules, patterns, and standard checksum algorithms — plus an optional expected amount range that warns (without blocking) when a value is unusually large or small for the field; share them with your team as files • See what it's caught: a running, local-only tally of the mismatches, bad values, account-change warnings, and page problems Double Check has flagged for you — real events, never an estimated dollar figure • Submit Guard (beta): optionally block a site's forms from submitting while a field you normally double-check there is unverified • Keyboard-first: invoke, verify, and attest without touching the mouse PRIVACY IS THE ARCHITECTURE, NOT A POLICY Double Check has no access to any page until you invoke it there — it requests no standing permission to read websites. Verified values are never transmitted, logged, or stored. OCR and speech recognition run entirely on your device. There are no analytics and no telemetry. The only network traffic is license verification with our payment provider. PRICING 7-day free trial with full features — no card required to start. Then $4.99/month, $39/year, or a $99 one-time lifetime license. Core double-entry checking keeps working even without an active subscription, because a safety check should never be held hostage. Outfitting a team? Email tmh@possibility.com about volume pricing. WHO IT'S FOR Accountants and bookkeepers entering wire details. Accounts-payable and treasury teams. Payroll. Paralegals filing with exact case numbers. Crypto users pasting addresses. Anyone who has ever stared at a routing number, looked away, looked back, and wished someone would check it with them. Double Check assists verification; responsibility for submitted values remains yours. It's the second pair of eyes — you're still the first.