Security advisory (updated 3 November 2026): a firmware flaw in some Coldcard models, disclosed in July 2026, produced seeds with far less randomness than intended. Coinkite has released fixed firmware for every affected model, but updating does not repair a seed created on affected firmware. If you created a seed on a Coldcard, read who is affected and exactly what to do, or use the two-minute check. All current advisories: security advisories.
The MK4 is discontinued. Coinkite no longer sells it; the Mk5 replaced it in March 2026 and runs the same firmware line (5.6.3 for both as of 3 November 2026). This guide has been updated for that firmware: you now install the update right after setting your PIN and before you create a seed (Step 5), and every new seed needs your own dice rolls, coin flips or key presses (Step 6). See the July 2026 advisory above.
If you have a Mk5: you can follow this guide. It runs the same firmware, and Coinkite says it is “100% backwards-compatible with your existing COLDCARD backups and workflows”, so the PIN, seed creation with dice, passphrase, trick PINs, microSD export and Sparrow steps below work the same way. What changes is the hardware: a larger 1.54-inch screen behind Gorilla Glass, a redesigned keypad, a more compact case, faster NFC and the USB-C port on the bottom. Where a menu name differs on your screen, follow the device. The Mk5 costs $269 ($219 on sale) in Coinkite’s store as of November 2026.
Coldcard MK4 Setup Guide 2026: Complete Step-by-Step Tutorial
The Coldcard MK4 was Coinkite’s main signing device until the Mk5 replaced it in March 2026. Built by Coinkite in Canada, it was designed from the ground up for Bitcoin-only users who prioritize air-gapped operation and advanced security features. This guide walks through every step of setting up a Coldcard MK4, from unboxing to signing your first transaction with Sparrow Wallet. Coinkite says the Mk5 is fully backwards-compatible with MK4 backups and workflows, but we wrote these steps for the MK4 and have not checked every screen against the Mk5.
If you are comparing hardware wallets before purchasing, our hardware wallet buying guide covers the full landscape of devices available in 2026. If this is your first hardware wallet, our lesson How to Set Up a Hardware Wallet explains each step in plain language.
Prerequisites: What You Need Before Starting
Gather everything before you begin. Interrupting the setup process midway is not ideal, especially during seed generation.
- Coldcard MK4 or Mk5 device — Coinkite no longer sells the MK4; if you are buying new, you will get a Mk5. Buy it new from Coinkite’s own store (store.coinkite.com). If Coinkite does not deliver to your country, use a reseller listed on its website and check our security advisories for that reseller first: in October 2026 an authorised reseller in Southeast Asia sold tampered Ledger and Trezor devices. Avoid Amazon, eBay and other marketplaces, even listings labelled “official store”, and never buy second-hand. The device should arrive in a tamper-evident bag with a unique bag number.
- MicroSD card — The Coldcard uses MicroSD for air-gapped communication with your computer. Coinkite supports cards of up to 32 GB formatted FAT32, so a small 8 GB or 16 GB card is plenty.
- USB-C cable or battery pack — The MK4 uses USB-C for power. For a fully air-gapped setup, power it from a USB battery pack or a wall charger instead of a computer. It needs power, not data, so any USB-C cable will do. Some “smart” battery packs switch themselves off because the Coldcard draws so little current; a wall charger avoids that.
- Computer with Sparrow Wallet installed — Sparrow is the recommended desktop wallet for use with Coldcard. Download it from sparrowwallet.com and verify it before installing: check the PGP signature on the release manifest, then check that the installer’s SHA-256 hash matches its line in that manifest. The signature covers the manifest, not the installer. Sparrow runs on Windows, macOS, and Linux.
- Metal seed backup device (recommended) — A steel plate or capsule for stamping or engraving your seed words. Paper backups degrade over time and are vulnerable to fire and water damage. Our guide on seed phrase storage best practices covers the options in detail.
Step-by-Step Coldcard MK4 Setup
Step 1: Verify the Tamper-Evident Bag
Your Coldcard MK4 ships inside a special tamper-evident bag with a unique number printed on it. Before opening, inspect the bag carefully. Look for any signs of tampering: tears, resealing marks, or discoloration along the edges. The bag is designed to show evidence of any opening attempt, but Coinkite warns that plastic bags can be defeated with a sharp knife or a heat press, so an intact bag is one layer of protection, not proof on its own.
Write down or photograph the bag number. The same number is printed on a tear-off tab sealed inside the bag, and Coinkite recorded it inside the device at the factory, so the Coldcard shows it on its screen when you first power it on (Step 2). All three must match. If the bag shows any signs of tampering, or the numbers differ, do not use the device. Contact Coinkite for a replacement.
Step 2: Power On the Device
Connect the Coldcard MK4 via USB-C to either a computer or a battery pack. If you plan to operate fully air-gapped (recommended), use the battery pack. The device will power on and display the Coinkite logo followed by the initial setup screen.
The MK4 features a sharp OLED screen and a full numeric keypad. Navigation uses the keypad numbers, the OK button (checkmark), and the X button (cancel). Spend a moment getting familiar with the button layout before proceeding.
Step 3: Accept Terms and Read Warnings
The Coldcard displays its terms of sale and a series of warnings about the nature of Bitcoin self-custody. Read through these carefully. The warnings explain that Coinkite cannot recover lost PINs or seed phrases, and that you are solely responsible for securing your backup. Press OK to acknowledge each screen.
This is not boilerplate to skip past. Understanding that there is no recovery service and no customer support backdoor is fundamental to using a hardware wallet properly. For deeper background on who holds the keys, see our lesson on custodial and non-custodial wallets.
Step 4: Set Your PIN
The Coldcard uses a two-part PIN system: a prefix and a suffix, separated by the device displaying two anti-phishing words. The words tell you whether you are typing into your own Coldcard or into a swapped or tampered lookalike built to capture your PIN.
How it works:
- Enter your PIN prefix (2-6 digits). Press OK.
- The Coldcard displays two unique words. These words are derived from your prefix and the device’s secure element. They will be the same every time you enter the correct prefix on this specific device. Memorize them.
- Enter your PIN suffix (2-6 digits). Press OK.
The anti-phishing words serve a critical purpose. If you power on your Coldcard and enter your prefix but see different words than expected, something is wrong — the device may have been swapped or tampered with. Do not enter your suffix.
Choose a PIN that is at least 4 digits for the prefix and 4 digits for the suffix (8 total). Avoid obvious patterns like 1234-5678. Coinkite allows only 13 wrong PIN attempts in a row (entering the correct PIN resets the count): after the 13th, the Coldcard bricks itself permanently, whatever your other settings, so brute force is impossible. That also means a forgotten PIN can’t be recovered, so a strong PIN you can remember matters.
Step 5: Update the Firmware Before You Create a Seed
Stop at the main menu once your PIN is set. Coinkite’s instructions are explicit: install and confirm the current firmware before you choose a seed or restore option, and do not generate or import a seed, restore a backup or fund the wallet until the update is done. Firmware updates require a PIN, which is why this step comes after Step 4. As of 3 November 2026 the current release for the MK4 and Mk5 is 5.6.3.
Check coldcard.com/downloads for the latest firmware. Download the .dfu file, verify the PGP signature on Coinkite’s signatures.txt with their public key, and check that the file’s SHA-256 hash matches its line in that list. Copy the verified file to your MicroSD card, insert it into the Coldcard and navigate to Advanced/Tools > Upgrade Firmware. The Coldcard verifies the firmware signature internally before applying the update. If the signature check fails, the update is rejected.
Step 6: Generate Your New Seed with Dice
On current firmware (5.6.1 and later) every new seed needs your own input as well as the device’s randomness. The Coldcard asks for one of three methods: at least 50 physical dice rolls, 128 coin flips, or 65 key presses with unpredictable timing. It mixes that input with fresh entropy from its hardware generator and both secure elements to produce a 24-word BIP39 seed phrase.
Choose dice, and roll at least 99 times. Ninety-nine rolls of a fair six-sided die carry about 256 bits of entropy, enough for a 24-word seed on their own, so your seed no longer rests on any vendor’s generator. Use a casino die if you have one, roll where nobody can watch, and never write the sequence down. Coinkite also offers a separate Dice Rolls Only path that hashes your rolls directly and uses no device randomness at all; its dice-roll documentation explains how it works.
On 5.6.2 and later you can also check the mix. View TRNG Words shows the device’s 256-bit input before your rolls go in, and Coinkite’s verify_seed_mix.py recomputes the final words on an offline computer (it works with dice or coin flips, not key presses). Run that check once on a wallet you never fund, then start again with fresh rolls for the real seed, because anyone holding both the TRNG words and your rolls can rebuild the wallet.
Why we insist on dice: in July 2026 a firmware bug left seeds generated on affected firmware, the MK4 included, with far less randomness than intended (see the advisory above). Coinkite puts affected MK4 seeds at about 72 bits instead of 128, and Block’s engineers found as few as 32 if an attacker can rebuild the device’s timers. Each bit fewer halves the number of guesses an attacker needs. The tradeoffs between different entropy sources are discussed in our complete guide to seed phrase security.
Step 7: Write Down Your 24-Word Seed Phrase
The Coldcard displays your 24-word seed phrase, a few words at a time. Write every word down on paper, clearly and in order. Number each word 1 through 24. Double-check your handwriting — a misread word during recovery will prevent access to your funds.
Use the paper backup as your working copy for the next step (verification). After verification, transfer the words to your metal backup device and check every word and its position against the paper. Then test the metal: under Advanced/Tools > Temporary Seed > Import Words, enter the words from the metal. The check passes only when the Coldcard refuses them because they are already its master seed (if it accepts them, choose Restore Master and find the mistake). Keep the paper until that check passes, then store it separately or destroy it, depending on your security model.
Never type your seed words into a computer, phone, or any internet-connected device. Never photograph them. Never store them in a password manager or cloud service.
Step 8: Verify Your Seed Phrase on Device
The Coldcard will quiz you on your seed words to confirm you wrote them down correctly. It asks for your words one position at a time, in random order, and offers three choices for each; you press the number of the right one. This step catches transcription errors before they become catastrophic.
A wrong choice makes the Coldcard ask for the same word again, and if you are unsure you can press OK to see the words again. Take this step seriously. A seed phrase with even one wrong word is unrecoverable without specialized tools, and even then recovery is not guaranteed.
Step 9 (Optional): Set Up a BIP39 Passphrase
A BIP39 passphrase (sometimes called the “25th word”) adds an extra layer of protection. Coinkite itself recommends a strong, unique passphrase for any wallet that holds an amount whose loss would be materially harmful to you, and we recommend one for any savings. When enabled, your 24-word seed plus the passphrase derive a completely different set of keys than the 24 words alone. Without the passphrase, an attacker who finds your seed words will access a wallet with no funds (or you can leave a small decoy amount).
To set this up, navigate to Passphrase in the Coldcard menu. You can use up to 100 characters of plain ASCII (no accented letters), and it is case-sensitive and space-sensitive. The Coldcard will show you the fingerprint of the resulting wallet. Write it down with your passphrase backup, so you can confirm it matches in your desktop software and check it each time you apply the passphrase.
The passphrase must be backed up separately from the seed phrase. If you forget it or lose it, the funds in the passphrase-protected wallet are gone. Our article on wallet security and passphrases covers the practical considerations of passphrase usage.
Step 10 (Optional): Set Up Trick PINs
The Coldcard MK4 supports Trick PINs — alternative PINs that trigger special behavior when entered. Two important ones:
Duress PIN: Opens a decoy wallet with a small balance. If someone forces you to unlock your Coldcard, you enter the duress PIN instead of your real PIN. The attacker sees a functional wallet and may believe they have accessed your funds. Load a small amount of Bitcoin into the duress wallet to make it convincing.
Brick PIN: Permanently destroys the secure element, making the device unusable. This is a last-resort option for extreme threat scenarios. Once triggered, the Coldcard cannot be recovered. Your funds remain safe as long as you have your seed phrase backup (and your passphrase, if you used one).
These features are configured under Settings > Login Settings > Trick PINs. Think carefully before enabling the brick PIN — accidental entry is permanent.
Step 11: Export Wallet to Sparrow via MicroSD
Insert your MicroSD card into the Coldcard. Navigate to Advanced/Tools > Export Wallet > Generic JSON. The Coldcard will write a file to the MicroSD card containing your wallet’s public key information (xpub). This file contains no private keys and is safe to transfer to your computer.
Remove the MicroSD card and insert it into your computer. This is the essence of air-gapped operation — the Coldcard never connects directly to your computer. All communication happens through the MicroSD card, and only public key data and unsigned/signed transactions are exchanged.
Step 12: Connect Sparrow Wallet (Import xpub)
Open Sparrow Wallet on your computer. Go to File > New Wallet, give it a name, and click Create Wallet. On the next screen, select “Airgapped Hardware Wallet” and then click “Import File.” Navigate to the JSON file on your MicroSD card and select it.
Sparrow will import the xpub and derive your wallet addresses. You should see the wallet fingerprint displayed — compare this with the fingerprint shown on your Coldcard under Advanced/Tools > View Identity. They must match. If they do not, something went wrong and you should start over.
Sparrow can now generate receive addresses, build unsigned transactions, and monitor your balance — all without the Coldcard being connected. The Coldcard is only needed to sign transactions.
Step 13: Receive Your First Transaction
In Sparrow, go to the Receive tab. You will see a Bitcoin address and QR code. Before sending any funds to this address, verify it on your Coldcard. Navigate to Address Explorer on the Coldcard and confirm the address matches what Sparrow displays.
This verification step is not optional. Malware on your computer could substitute a different address in Sparrow’s display. The Coldcard’s screen is the source of truth. If you use a passphrase, test it before any coin moves: unplug the Coldcard and power it back on, enter the passphrase again from your written copy and confirm it shows the same fingerprint as Sparrow. Send a small test amount first, confirm it arrives, and keep the balance that small until recovery works: restore the wallet from your seed backup and your exact passphrase, if you use one (on a spare or wiped device if you can), check that it shows the same fingerprint and the same first addresses, and sign the Step 14 test spend from the restored wallet.
Step 14: Send a Test Transaction (PSBT Signing via MicroSD)
To send Bitcoin, build the transaction in Sparrow as normal — enter the destination address and amount. Instead of signing directly, Sparrow will create a PSBT (Partially Signed Bitcoin Transaction) file. Save this file to your MicroSD card.
Insert the MicroSD into your Coldcard and choose Ready To Sign. The device opens the PSBT file and displays the transaction details: destination address, amount, fee, and change address. Verify everything on the Coldcard screen. If it looks correct, approve and sign. The Coldcard writes the signed transaction back to the MicroSD card.
Move the MicroSD back to your computer, click “Load Transaction” in Sparrow and select the signed PSBT file. Click “Broadcast Transaction” to send it to the Bitcoin network. At no point did the Coldcard’s private keys leave the device or connect to the internet.
Step 15: Keep the Firmware Current
Repeat the update from Step 5 whenever Coinkite publishes a new release, and read its notes first: Coinkite asks owners to treat every applicable Coldcard firmware release as a critical update. Updates do not erase your seed phrase, and they do not repair a seed that was created on older firmware. It is still good practice to check that your backups are accessible before any update. For a broader discussion of firmware security across devices, see our article on firmware updates and security best practices.
Air-Gapped vs USB Operation
The Coldcard MK4 supports both air-gapped (MicroSD) and USB-connected operation. It can also sign by an NFC tap from a phone, but NFC is off by default and this guide does not use it. Here is how the card and the cable compare:
Air-gapped (recommended): The Coldcard never physically connects to a computer. Power comes from a battery pack. Transaction data moves via MicroSD card. This eliminates entire categories of attack — USB-based exploits, malicious HID commands, and data exfiltration over the wire are all impossible. The tradeoff is a slightly slower workflow since you are physically moving the MicroSD card back and forth.
USB-connected: The Coldcard connects to your computer via USB-C and communicates with Sparrow directly. Transaction signing is faster since you do not need to shuffle the MicroSD card. However, this exposes the device to USB-layer attacks and requires trusting the USB stack on both the Coldcard and your computer. The Coldcard lets you narrow that exposure: its Virtual Disk mode, which makes it appear to the computer as a USB drive, is off by default, and Settings > Hardware On/Off > USB Port turns the USB data link off altogether. Air-gapped operation removes the attack surface entirely.
For long-term cold storage, use air-gapped operation. For more frequent spending from a smaller balance, USB operation with Sparrow is a reasonable convenience tradeoff. Our comparison of cold storage versus hot wallet architectures helps frame when each approach is appropriate.
Security Tips
- Store the Coldcard separately from your seed backup. If both are in the same location, a single theft or disaster compromises everything.
- Use the duress PIN. Load a small amount of Bitcoin into the duress wallet. If coerced, enter this PIN and hand over the device. The attacker sees a real wallet with real funds.
- Consider a passphrase for large holdings. Your seed backup alone will not access the funds — the attacker also needs the passphrase, which is stored separately.
- Verify addresses every time. Always check receive and send addresses on the Coldcard screen, not just in Sparrow.
- Keep firmware updated. Subscribe to Coinkite’s announcements or check their site monthly for security updates.
- Use a dedicated MicroSD card. Do not reuse it for other devices. Label it and store it with your Coldcard.
- Consider multisig for larger amounts. A single-signature setup, even with a Coldcard, is a single point of failure. For savings we recommend a 2-of-3 with devices from three different manufacturers (see our 2-of-3 setup guide). Our guide on transitioning from singlesig to multisig explains when and how to upgrade.
Troubleshooting Common Issues
Coldcard does not power on via USB-C: Try a different cable or power source. The MK4 needs power, not data, so any USB-C cable works, including power-only ones. If a battery pack keeps switching off, it may be a “smart” pack that cuts out at very low current; use a wall charger instead.
Sparrow does not recognize the wallet file: Ensure you exported as “Generic JSON” from the Coldcard, not one of the other formats. Also confirm you are importing into a new wallet in Sparrow, not trying to load it into an existing wallet.
Address mismatch between Coldcard and Sparrow: Check that Sparrow is using the correct derivation path. For native SegWit (recommended), the path should be m/84'/0'/0'. If you set up a passphrase on the Coldcard, make sure it is active when checking the address explorer.
PSBT file not detected by Coldcard: The file must have a .psbt extension and be in the root directory of the MicroSD card (not in a subfolder). Also verify the MicroSD card is formatted as FAT32, not exFAT or NTFS, and is no larger than 32 GB.
Forgot PIN: There is no recovery. After 13 wrong attempts in a row the Coldcard bricks itself permanently, whatever your settings. Your funds are recoverable only if you have your seed phrase backup (and your passphrase, if you used one). Restore it on a new Coldcard (Mk5 or Q) or another wallet that accepts BIP39 words.
Frequently Asked Questions
Can I use Coldcard MK4 with wallets other than Sparrow?
Yes. The Coldcard MK4 works with any wallet software that supports PSBTs and can import xpub data. Popular options include Electrum, Specter Desktop, Nunchuk, and BlueWallet (watch-only). Sparrow is recommended because of its strong air-gapped workflow support and detailed PSBT handling, but it is not required. The export menu on the Coldcard includes presets for multiple wallet applications. To pair it with Electrum, follow our lesson Electrum Wallet: The Complete Guide.
Is the Coldcard MK4 seed generation truly random?
Not on every firmware version. In July 2026 Coinkite disclosed a firmware bug that left seeds generated on several Coldcard models, the MK4 included, with far less randomness than intended until fixed firmware shipped (5.6.0 for the MK4). Coinkite’s advisory puts affected MK4 seeds at about 72 bits of entropy instead of 128. On current firmware (5.6.1 and later) every new seed requires your own entropy, from dice, coin flips or key presses, which the device mixes with its hardware generator and both secure elements, and 5.6.2 lets you verify that mix offline. We recommend 99+ dice rolls for any seed that will hold savings. If your seed was created on older firmware, read our advisory on who is affected and what to do.
What happens if Coinkite goes out of business?
Your Bitcoin remains accessible because the Coldcard uses standard BIP39 seed phrases and standard derivation paths (BIP44/49/84/86). You can restore your wallet on any compatible hardware or software wallet. The firmware’s source code is public (MIT licence with a “Commons Clause” that forbids selling it), so others could keep maintaining it. Your seed phrase, plus your passphrase if you used one, is your true backup — the Coldcard is just a signing device. Our lesson on what a Bitcoin wallet is explains why: a wallet holds keys, not coins.
Should I use the Coldcard MK4 in a multisig setup?
For amounts that would significantly impact your financial life if lost or stolen, yes. A multisig configuration — typically 2-of-3 — means no single device compromise can result in loss of funds. The Coldcard MK4 works well in multisig setups with Sparrow, Specter, or Nunchuk as the coordinator. Pair it with devices from two other manufacturers (for example a Trezor and a Jade) for hardware diversity, and generate every seed with 99+ dice rolls. For single-signature setups on moderate amounts, the Coldcard alone with a passphrase provides a strong security profile.
