One transposed digit in a wire transfer sends money to the wrong account. Double Check turns the careful-but-manual ritual — read it, re-read it, ask a colleague to look over your shoulder — into a fast, verifiable workflow that happens right in the field you’re typing into.
How it works
Invoke it on the field
Click into the field and press ⇧⌘Space (Shift+Command+Space; Ctrl+Shift+Space elsewhere) — or right-click → “Double-check this field”.
Two independent readings
The format is detected and its math verified instantly. Then re-type the value from your source — or scan it, paste a screenshot, or read it aloud.
Green, attested, logged
A match goes green; you attest; the check is logged (never the value) and the field gets a badge that flips to a warning if anything changes it afterwards.
It explains the mistake, not just flags it
Transposed digits are the classic transcription error — so they get called out by name, with a character-level diff:
Everything it does
Real checksum math, not just patterns
23 built-in formats. Routing numbers, IBANs, cards, CLABE, CUSIP, ISIN, VINs, and crypto addresses carry internal check digits — Double Check computes them, so a single wrong digit is often caught before you re-type anything.
Blind double entry
Re-type the value from your source — not from the field. Two independent readings must agree. Empty fields get a safe two-step entry flow.
Amounts taken seriously
US and European separators both parse; ambiguous amounts like “1,234” are refused rather than guessed. Matches confirm in words: one million two hundred thousand and 00/100.
Compare against an image
Scan a screen region or paste a screenshot or phone photo. A bundled OCR engine reads it on your device — images are never uploaded.
Speak it
Read the value aloud from the paper in your hand; Chrome’s on-device speech recognition transcribes it (Chrome 139+). No audio ever leaves your machine.
Hear it read back
A local on-device voice reads the value digit by digit, at the speed you choose — read along on your source.
A badge that stays honest
Verified fields get a “Double-Checked” badge. If the value changes afterwards — any reason, any keystroke — it flips to a warning and the log entry is marked stale.
Proof without the value
Every attested check is logged: when, where, what format, which methods, your attestation — never the value itself. Export CSV/JSON for your records.
It remembers each site
Confirm a field is an IBAN once and the right format is preselected on that site forever after.
Your own formats
Vendor IDs, policy numbers, internal schemes — defined as data (patterns, lengths, checksum algorithms), never code, and shareable with your team as files.
Submit Guardbeta
Flip it on for a site and its forms won’t submit while a field you double-check there is unverified or was edited after checking.
Keyboard-first
Invoke, verify, and attest without touching the mouse. Built for people who enter numbers all day.
Pricing
Cancel anytime.
Two months free. The plan most people pick.
For people who hate subscriptions.
Every plan starts with a 7-day free trial — full features, no card required. And core double-entry checking keeps working even without a subscription, because a safety check should never be held hostage.
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.