The COLDCARD Mk4 firmware is open source and can be found on Github. In the past, Coinkite also shared the hardware design of their hardware wallet. However, it's worth mentioning that since 2022, Coldcard no longer explicitly refers to their firmware as open source on their webpage. Instead, they use the term "verifiable source code." This change is due to the inclusion of a common clause in their license that restricts commercial use. The decision was made after another company allegedly copied portions of COLDCARD's code to promote their own hardware wallet.