what's COLDCARD?

COLDCARD is an air-gapped Bitcoin-only hardware wallet focused on maximum security for signing transactions. It uses PSBT (Partially Signed Bitcoin Transactions) for seamless multisig and air-gapped workflows via SD cards or QR codes, eliminating USB connections and companion apps. Key features include duress/decoy PINs, tamper-evident clear cases, anti-phishing mechanisms, and an address explorer for verifying balances offline without trusting software. Developed by Coinkite, it supports advanced standards like BIP-85 for deriving child seeds, BIP-39 passphrases, and integrates with wallets such as Sparrow, Electrum, and BlueWallet. Models like Mk4 and flagship COLDCARD Q offer battery power, dual SD slots, QWERTY keyboard, and QR scanner, prioritizing simplicity and paranoia-level security for self-custody.

COLDCARD launches its Mk5 hardware wallet device.