Coinkite releases NFC PushTx for COLDCARD Mk4 and Q — tap your COLDCARD to your phone to broadcast a signed Bitcoin transaction directly to the blockchain. No apps, no computer, no wallet software required.
PushTx encodes the complete signed transaction into a URL served over NFC. When you tap your phone on the COLDCARD, your browser opens and the transaction is immediately broadcast via mempool.space or coldcard.com. It's the simplest possible path from air-gapped signing to on-chain confirmation — one tap.
Disclosure: Coinkite Inc. is the maker of this product and the publisher of this site.
coldcard.com/pushtx