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What is DoublyCheck?

DoublyCheck is a handy verification tool for crypto wallets and IBANs. Point your camera at any address to scan it, then compare it against your saved address book or a second source. It keeps a private, encrypted record of your trusted addresses on-device — no accounts, no cloud, just a straightforward way to send with confidence.

How does address book matching work?

You build your address book by scanning a QR code, scanning plain text with the camera, or entering an address manually. Each entry gets a label — for example "Exchange Wallet" or "Personal Ledger". When you later scan an incoming address, DoublyCheck automatically cross-references it against your saved entries and tells you if there's a match, giving you a confirmed identity for the recipient before you send anything.

What is clipboard hijacking and how does DoublyCheck stop it?

Clipboard hijacking malware silently replaces a copied address with an attacker-controlled look-alike the moment you paste. These swapped addresses often share the same start and end characters as the real one, making them hard to catch by eye. DoublyCheck's dual-scan workflow defeats this: scan the destination address shown on screen, then scan your original source (a hardware wallet display, a paper backup, or a trusted saved entry). The app performs a character-by-character comparison and immediately alerts you to any discrepancy — including look-alike attempts that only change characters in the middle.

Does DoublyCheck remember addresses I've scanned before?

Yes. Every scan is saved on-device with a timestamp. If you scan an address you've interacted with previously, DoublyCheck shows you when you first saw it and when you last scanned it. This historical consistency gives you an extra layer of confidence — if an address you've sent to dozens of times suddenly looks unfamiliar, that's a signal worth investigating.

Is this better than a regular scanner? And what if it misreads a character?

DoublyCheck is not designed to scan an address and have you copy-paste the result into your wallet. The point is comparison — scanning two sources and confirming they match, or matching against an address you already saved and trust.

For Bitcoin, Ethereum, and IBAN addresses, DoublyCheck validates the built-in checksum after every scan. This automatically catches AI misreads — a garbled character will almost always break the checksum, and the app tells you the address is structurally invalid before the comparison even runs. After that, it checks whether the scanned address is in your address book, or compares it against a second scan from another source.

Good use cases: catching clipboard hijackers that silently swap your copied address, catching copy/paste errors, comparing the address on your hardware wallet or paper backup with the recipient field in another app to confirm nothing was swapped, and using your labelled address book to spot when you've accidentally selected the wrong recipient.

Not a good fit: do not scan an address and then use the scan result as the address to send money to — that inverts the whole idea. The app is for verifying that two sources match, not for extracting an address for you. Similarly, do not type an address manually and expect DoublyCheck to catch your typo.

Is my data safe?

All data stays on your device. There are no cloud servers, no accounts, and no data collection. Your address book is encrypted locally and excluded from device backups.

What address formats are supported?

DoublyCheck supports Bitcoin addresses (Legacy, SegWit, and Bech32), Ethereum addresses, and IBANs. Checksum validation is built in for supported formats.

Can DoublyCheck send or receive funds?

No. DoublyCheck is a verification tool only. It cannot send, receive, or store any cryptocurrency or funds. It is not a wallet or an exchange.

You misspelled your app

Dammit! Wish there had been an app to warn me before I bought the domain.

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