description Coldcard Mk4 Overview
The Coldcard Mk4 is a highly secure, air-gapped hardware wallet primarily designed for Bitcoin enthusiasts. Its air-gapped nature means it never connects directly to the internet, minimizing attack vectors. Transactions are signed on the device and transferred via microSD card. It features a powerful microcontroller and supports advanced features like multisig and passphrase recovery.
While it's Bitcoin-only, its robust security and customizable options appeal to users prioritizing maximum security. The learning curve is steeper than some other wallets, but the enhanced security is a significant benefit.
info Coldcard Mk4 Specifications
| Input | 2-button navigation with distinct click and hold actions |
| Weight | 26 grams |
| Display | 128x64 pixel OLED monochrome screen |
| Materials | Polycarbonate body with metal insert for durability |
| Dimensions | 85.6mm x 54mm x 6mm (credit card form factor) |
| Connectivity | USB-C (charging only, no data), microSD slot |
| Power Supply | USB-C (no internal battery) |
| Certification | CC EAL5+ certified secure element |
| Security Chip | ATECC608B secure element |
| Supported Cryptocurrencies | Bitcoin (default), limited multi-coin firmware available |
balance Coldcard Mk4 Pros & Cons
- Air-gapped design ensures private keys never touch an internet-connected device
- Open-source firmware allows independent security audits and community verification
- Secure element (ATECC608B) provides tamper-resistant key storage
- Durable hardware with no wireless connectivity, eliminating RF attack vectors
- Supports PSBT (Partially Signed Bitcoin Transactions) for multi-signature setups
- Anti-phishing word lists protect against malware-in-the-middle attacks during setup
- Bitcoin-only by default; requires separate firmware for limited altcoin support
- Steeper learning curve compared to plug-and-play wallets like Ledger or Trezor
- No wireless connectivity means all transfers require physical microSD card handling
- No touch screen; navigation relies on two-button interface which some find tedious
- Lacks built-in exchange integration, requiring external services for swaps
help Coldcard Mk4 FAQ
Is the Coldcard Mk4 truly air-gapped or can it connect to the internet?
The Coldcard Mk4 has zero network hardwareno WiFi, Bluetooth, or Ethernet. It cannot initiate any internet connection. All data transfer occurs exclusively via microSD card, making it a true air-gapped device for maximum isolation of private keys.
How do I sign and broadcast a Bitcoin transaction with the Coldcard Mk4?
Create an unsigned transaction in your connected wallet software, export it to microSD, insert the card into Coldcard, review transaction details on its screen, approve with your PIN, and export the signed transaction back to microSD. Then broadcast via your connected computer or a full node.
Can the Coldcard Mk4 store Ethereum, Solana, or other altcoins?
The Coldcard is primarily designed for Bitcoin. While a multi-coin firmware exists, it offers limited altcoin support and is generally not recommended. For Ethereum or other major altcoins, dedicated wallets or hardware wallets with broader coin support may be more suitable.
Is the Coldcard Mk4 firmware open-source and auditable?
Yes, Coinkite has released the Coldcard firmware as open-source under a permissive license. Users can review, compile, and verify the code themselves, ensuring no backdoors or hidden functionality compromise security. This transparency is a core design philosophy.
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What are the key specifications of Coldcard Mk4?
- Input: 2-button navigation with distinct click and hold actions
- Weight: 26 grams
- Display: 128x64 pixel OLED monochrome screen
- Materials: Polycarbonate body with metal insert for durability
- Dimensions: 85.6mm x 54mm x 6mm (credit card form factor)
- Connectivity: USB-C (charging only, no data), microSD slot
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