The Coldcard (Mk1, Mk2, Mk3 and MK4) is a Bitcoin, open-source, hardware wallet designed with security in mind. The device enables you to set up a wallet, send funds and store bitcoin while offering a proficient user display and interface. Security considerations transmit throughout the packaging process. The Coldcard comes in a sealed plastic bag with a number on it, the same number is also engraved permanently on the ColdCard board. Due to the transparent case, the number can be seen interiorly and should match the one displayed on the bag.

The Coldcard uses a Micro-SD card to back up the seed phrase as well as send outbound, signed Bitcoin transactions without having to connect to the internet. If full internet privacy is not an issue for the owner, the NFC integration can be used to tap the Coldcard against their mobile phone to complete a Partially Signed Bitcoin Transaction. This feature is optional and can be disabled. The Micro-SD card can also be used in conjunction with cold storage software supported by Coldcard. Compatible wallets include, BlueWallet, Wasabi wallet and the Bitcoin Core wallet feature.

Users generally own the ColdCard MK2 and Mk3 and these versions are the most recommended as they fulfil most of the user’s needs. However, with the recent release of the Coldcard Mk4 version, it has been identified that the most significant difference is the additional security features, extra memory, and the added NFC feature. Although for first time users it could be regarded as complicated to use, it is a general agreement from the more expert users that the ColdCard functions well as a signing device and a Bitcoin storage device. It also appears to satisfyingly integrate well with an Electrum server and Bitcoin Core, proving to be a very trusting hardware solution. In terms of security, the ColdCard is rated very high and, with CoinKite being one of the most established companies providing Bitcoin solutions, products produced by this company are very respected.