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NO APP LOCK-IN

Use any compatible wallet app. COLDCARD does the signing.

No COLDCARD account, no cloud wallet, no required companion app. Build the transaction in a compatible wallet, review it on COLDCARD, sign, and broadcast from the wallet.

Compatible wallets PSBT signing docs

How it works

Wallet app

Sparrow, Cove, Nunchuk, Specter, or another compatible wallet tracks addresses, balances, labels, fees, and history.

PSBT

The wallet creates a Partially Signed Bitcoin Transaction: an unsigned transaction waiting for COLDCARD's signature.

Signer

COLDCARD holds the private keys, shows the transaction on its own screen, signs if you approve, and returns the signed result.

Basic workflow

  1. Export a wallet file or descriptor.

    The wallet app learns public wallet data so it can show receive addresses and balances. It does not get the seed.

  2. Verify receive addresses on COLDCARD.

    Do not trust the phone or computer by itself. The address on COLDCARD is the one that matters.

  3. Build the transaction externally.

    Choose coins, destination, and fee in the wallet app. Save or display the unsigned PSBT.

  4. Move the PSBT to COLDCARD.

    Use MicroSD, Virtual Disk, NFC, or QR on Q. Strict air-gap users use MicroSD or QR.

  5. Review before signing.

    Check amount, destination, fee, and change on the COLDCARD screen. If it looks wrong, reject it.

  6. Return and broadcast.

    The wallet app broadcasts the signed transaction. COLDCARD never needed an account or cloud service.

Useful does not mean trusted.

A phone or computer wallet can help with fees, labels, and history. It can also be wrong or compromised. Verify addresses and transaction details on COLDCARD.

Compatible wallets Ready To Sign Descriptor export