Coldcard Mk4
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Coldcard Mk4 is the reference device for Bitcoin self-custody specialists: it signs transactions entirely via QR or microSD with no USB data connection, supports native multisig coordination with PSBT, and runs fully ope
A-Best for Bitcoin Security
Coldcard Mk4 is the reference device for Bitcoin self-custody specialists: it signs transactions entirely via QR or microSD with no USB data connection, supports native multisig coordination with PSBT, and runs fully open-source firmware on dual secure elements (ATECC608B + the new SE2 chip). The numeric-keypad-only interface is deliberately spartan — this is a deliberate security tool, not a consumer gadget, and it rewards users who take time to learn it.
Pros
- True air-gap via QR or microSD — never connects to the internet
- Industry-leading multisig and PSBT tooling
- Dual secure element design with fully open-source firmware
Cons
- Bitcoin-only — no Ethereum or altcoin support
- Steep learning curve; spartan UI not beginner-friendly
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