Coldcard MK4 - Bitcoin Hardware Wallet - various colors

Important: update the firmware before first use

This Coldcard Mk4 ships with an older firmware. In July 2026 Coinkite disclosed a flaw in the seed generation of these versions. Instead of its hardware random number generator, the device fell back to a predictable software source. A seed created this way is much weaker than intended. The hardware itself is fine, and the current firmware fixes the flaw.

How to set up your Coldcard Mk4 safely:

1. Check the sealed bag for damage, set your PIN and then stay in the main menu. Do not create or import a seed yet.
2. Download the current firmware from coldcard.com/downloads onto a microSD card. As of October 2026 this is version 5.6.3.
3. Install the update from the microSD card and check the version number on the display afterwards.
4. Only now create your seed. The current firmware also asks you for your own randomness, for example dice rolls.

With at least 50 rolls of a real die, your rolls alone carry 128 bits of entropy. Your seed then no longer depends on the device's random number generator. The Coldcard takes the rolls straight from its keypad. Our guide Roll your own Bitcoin seed explains what matters when rolling. We sell suitable dice as casino precision dice in a set of five. A microSD card is not included. For the update the Lexar Blue Plus 32 GB is all you need.

If you already created a seed on a Coldcard with older firmware, the update does not make it safer. Our guide to the Coldcard vulnerability explains what to do next.

The Coldcard Mk4 is the predecessor of the Mk5 and runs exactly the same firmware, so it keeps getting every update. You sign your transactions offline and move them by microSD card or NFC. Your private keys never leave the device.

Product details

• two secure elements from two different manufacturers
• trick PINs for duress situations, for example a PIN that opens a decoy wallet or wipes the seed
• tap-to-send NFC for transactions, addresses and XPUBs
• USB-C and a microSD slot
• USB disk mode: on a computer or phone the Coldcard shows up as a 4 MB drive
• 120 MHz processor, transactions up to 2 MB
• sliding cover protects display and keys
• size with cover 88 × 52 × 10 mm, weight about 30 g
• works with Sparrow, Electrum, Nunchuk and other wallets, multisig included

In the box

• Coldcard Mk4 in a sealed tamper-evident bag

Good to know: the Coldcard handles Bitcoin only, no other coins. It has no battery and needs power over USB-C to sign. If you want it to have no data connection to your computer, power it from a power bank. The Mk5 has a larger display under Gorilla Glass and a tougher case. Under the hood both do the same.

Buy your Coldcard Mk4 at Copiaro. Update first, seed second. Stay humble, stack sats.