ShopApplies to: COLDCARD Q, Mk5, and Mk4; QR scanning requires Q
Verified on: August 17, 2026
COLDCARD signs Partially Signed Bitcoin Transactions (PSBTs) created by compatible coordinator software. Choose a transport supported by both your COLDCARD model and the coordinator, then verify destination, amount, fee, and change on the COLDCARD screen before approving.
Signing and transaction review
Start here for the complete PSBT import, on-device review, signing, and return flow.
QR and BBQr on Q
Use the Q camera and display to transfer a PSBT without a cable or removable card.
MicroSD
Move the unsigned and signed PSBT between a computer and COLDCARD with a MicroSD card.
NFC
Use a compatible mobile coordinator to transfer the PSBT by tap when NFC is enabled.
An air gap changes how data crosses between devices; it does not make transaction review optional. Refuse the transaction if the on-device details do not match what you intended. Current standard firmware rechecks the staged PSBT immediately before signing and stops with Transaction modified if the reviewed bytes changed. Rebuild and review the transaction rather than retrying it.