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Hardware Features


The buttons on Mk4 should be self explanitory, with one exception: X is for Cancel/Refuse/Back and is called OK/Accept in the on-screen prompts.

MicroSD Cards#

  • Cards up to 32 GB are supported. Format must be either FAT12 or FAT32.
  • For best performance and long life, we recommend our specialized cards, available on our store, with SLC (single level cells) and higher endurance.
  • Since our storage needs are very modest, smaller cards are fine.
  • We cannot guarantee support for all MicroSD cards, current or future.
  • COLCARD Q: Two slots, called A and B are present. The top slot is A and acts as the default slot. When a single card is inserted (in either slot), then it is used without prompting. In some cases, and especially if two cards are present, then you may need to select using the (A) or (B) keys as shown on-screen.

USB Cable Required for Power#

  • Use a USB-C cable to connect to a computer or battery pack.
  • We strongly recommend using a COLDPOWER™ adapter, battery pack or AC adapter during setup and seed choosing.
  • Some battery packs may power down because the COLDCARD® draws very little current, and the pack thinks the attached device is "done charging". It's best to avoid these "smarter" battery packs. Wall adapters (AC to USB) work well.

Genuine / Caution Lights#

There are two lights (LEDs) marked as Genuine (green) and Caution (red). These lights are directly connected to the COLDCARD's Secure Element. Their purpose is to indicate the flash contents have not changed since your last use of the COLDCARD.

When you power up the COLDCARD, you should see a Verifying... screen and then the green (genuine) LED will light. This means the flash memory has the correct contents. There is no way for trojan software to change this light to green without your PIN.

Obviously, the COLDCARD from the factory will have a green light, and after each firmware upgrade, we update the checksum that is performed so the light will be green again. The only time you should see a red light is briedly during power-up sequence when the verification is on-going.


Do not enter your PIN code into what might look like your COLDCARD if the light is red! You should assume someone has tampered with its firmware, and it might operate normally, but in fact be trying to steal your money.

For more technical background on this security feature please have a look at this whitepaper.