Double Check - Wire, IBAN & Crypto Verifier

Double Check is a browser extension that prevents data-entry errors by mathematically validating high-stakes numbers and requiring you to independently retype them for a direct, on-site comparison within a website's input field. It specifically catches simple transcription errors, such as transposed digits, while also guarding against deliberate fraud, such as fake "changed bank details" emails and hidden look-alike characters Double Check is 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. Never second-guess a high-stakes transfer again. Double Check is a privacy-first browser extension that instantly verifies wire routing numbers, IBANs, and crypto addresses directly on your screen. Built for accounting professionals and crypto users who can't afford a single typo, our tool acts as an automated safety net for your most critical data entry. Best of all? It runs 100% locally with zero telemetry, guaranteeing your sensitive financial data never leaves your device. 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 • Built-in checks for the values that hurt most to get wrong — bank and wire details, payment cards, government and tax IDs, securities and vehicle identifiers, crypto wallet addresses, and contact and currency fields. Each is verified the way its format is actually defined, not matched against a loose pattern. • 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 international bank and wire 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 • Catch a secret before it leaves: the page audit also flags an API key, private key, or crypto seed phrase sitting in a field — including chat composers like ChatGPT's — and Submit Guard blocks a form carrying one (override with a second click; you stay in charge). Detection anchors on real structure, so git hashes and ordinary text are never flagged, and the secret itself is never stored or logged 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, …