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Ultra-secure, air-gapped Bitcoin storage trusted by security professionals.

The Coldcard Mk4 is a powerful Bitcoin-only hardware wallet built for maximum security and complete self-custody of your digital assets. Developed by Coinkite, the Coldcard Mk4 allows users to securely generate, store, and sign Bitcoin transactions without exposing private keys to internet-connected devices.

Unlike many hardware wallets that rely on USB or Bluetooth connections, Coldcard Mk4 supports fully air-gapped transaction signing via microSD card, significantly reducing the risk of malware or remote attacks.

Built with advanced security features such as secure element chips, tamper detection, and open-source firmware, the Coldcard Mk4 is widely regarded as one of the most trusted Bitcoin hardware wallets available today.

Perfect for both experienced Bitcoin users and those serious about long-term cold storage, Coldcard Mk4 delivers institution-grade protection in a compact device.

Why Choose Coldcard Mk4

• True air-gapped Bitcoin security using microSD transaction signing

• Bitcoin-only firmware for maximum security and simplicity

• Secure element chip protection against physical extraction attacks

• Open-source firmware with reproducible builds for transparency

• Advanced passphrase and seed management options

• Compatible with leading Bitcoin wallets and multisig setups

Coldcard Mk4 is designed specifically for Bitcoin self-custody, making it a preferred wallet among security experts, developers, and long-term investors.

Advanced Security Architecture

Coldcard Mk4 includes multiple layers of protection to safeguard your Bitcoin from digital and physical threats.

Secure Element Chip

• Dedicated hardware chip protects PIN verification and critical operations

• Prevents extraction of private keys through hardware attacks

Air-Gapped Transaction Signing

• Sign transactions using microSD card PSBT workflow

• No need to connect the device to an internet-connected computer

Anti-Tamper Design

• Hardware protections detect physical interference attempts

• Ensures keys remain secure even if the device is compromised

Open-Source Firmware

• Publicly auditable code allows independent verification of wallet security

Brick-Me PIN Option

• Emergency PIN permanently disables the wallet if accessed by an attacker

Air-Gapped Bitcoin Transactions

Coldcard Mk4 supports offline signing, one of the safest ways to manage Bitcoin.

MicroSD Workflow

1. Create a transaction using compatible wallet software

2. Export the transaction file (PSBT) to a microSD card

3. Insert the card into Coldcard Mk4

4. Sign the transaction securely offline

5. Move the signed transaction back to your computer to broadcast

This process ensures your private keys never touch an internet-connected device.

Bitcoin-Only Security

Coldcard Mk4 focuses exclusively on Bitcoin, which improves security and reliability.

Advantages of Bitcoin-only design include:

• Smaller attack surface compared to multi-coin wallets

• Simpler firmware and easier security auditing

• Faster updates focused purely on Bitcoin security

• Strong compatibility with advanced Bitcoin wallet tools

Supported wallet integrations include:

• Sparrow Wallet

• Electrum

• Specter Desktop

• Nunchuk

• Bitcoin Core

Key Features

• Bitcoin-only hardware wallet

• Air-gapped transaction signing using microSD

• Secure element chip protection

• Open-source firmware

• Multisignature wallet support

• Advanced passphrase and seed management

• Tamper-resistant hardware design

• PSBT transaction workflow

• Compact and portable design

• Brick-Me self-destruct security option

What’s in the Box

• Coldcard Mk4 Hardware Wallet

• Protective case

• USB cable

• Quick start guide

• Security instructions