CRYPTO GUIDANCE INC.

Kansas City, MO

What Is a PSBT?

Published 2026-08-15. Last updated 2026-08-15. Written by John Alewine, Crypto Guidance Inc.

A PSBT, partially signed Bitcoin transaction, is a file that describes a Bitcoin send before it is finished. A watch-only wallet on your computer builds the file: inputs, outputs, change, fee. You carry that file to a signing device that holds the keys. The device shows the amounts and addresses, you click yes, the file comes back signed, and the computer broadcasts it. The seed never visited the machine that has Slack open.

Who This Is For

Anyone using Sparrow with a Coldcard or another air-gapped signer. It is not a concept you need before your first Coinbase buy. It is the plumbing behind "how does the steel brick talk to the laptop."

How It Actually Works

The unsigned PSBT can travel on a MicroSD card, a QR code, or (less ideally) a USB cable. The format is standardized, which is why different wallets can cooperate.
Multisig is the other reason PSBTs exist: each key holder signs the same file in turn. See multisig.
If the device screen does not match what you thought you built, you refuse. That check is the whole security model. Signing blind is how people pay the wrong address.

Risks I See in Sessions

Trusting the computer preview and not reading the hardware screen. The computer can lie. The air-gapped screen is the one that counts.
Leaving signed PSBTs on a shared SD card. A signed file is a live check. Broadcast or delete it.

When It Matters

The day you graduate from "USB hardware wallet with a helper app" to a setup you want to keep for years. Pair with air gap and coin control.