COLDCARD

COLDCARD is a Bitcoin-only hardware wallet developed by Coinkite, a company based in Canada. Designed for users who prioritize deep security and full sovereignty over their funds, COLDCARD supports only Bitcoin and is built around an entirely air-gapped workflow: the device never needs to connect to a computer or the internet during its operational lifetime.

The current lineup includes two active product lines. The COLDCARD Mk5 is the latest compact model, featuring a 1.54-inch Gorilla Glass display, a redesigned tactile keypad, USB-C connectivity, and enhanced NFC for faster wireless transfers. It runs the same firmware as the Mk4, ensuring full feature parity and upgrade continuity. The COLDCARD Q is the larger flagship model, featuring a full QWERTY keyboard, a 320×240 LCD screen, dual MicroSD slots, an integrated QR code scanner with LED illumination, and the option to run on three AAA batteries for fully cable-free operation.

All models use dual secure elements sourced from two different manufacturers (Microchip ATECC608 and Maxim DS28C36B), storing private keys in dedicated hardware rather than in the main processor. Transaction signing relies on the PSBT (BIP174) standard, ensuring compatibility with coordinator software including Bitcoin Core, Electrum, and Sparrow. Transactions are transferred via MicroSD card, NFC, or QR code depending on the model.

Additional features include duress PIN options, BIP39 passphrase (25th word) support, encrypted MicroSD backups with verifiable integrity, and native multisignature wallet support. All COLDCARD firmware is fully open source, published on GitHub and designed to be reproducible, so users can independently verify that the code on their device matches the published source.