Library · Crypto, word by word · Inside Bitcoin
What is a PSBT?
A PSBT, or Partially Signed Bitcoin Transaction, is a standard format (BIP-174) for passing an unsigned or half-signed transaction between wallets and devices. It lets a hardware wallet or offline computer sign without going online, and lets several people add their signatures to one multisig payment.
What it means for you
Because the file carries the coins being spent and the scripts involved, the device holding your keys can check what it is signing instead of taking the online computer's word for it. Once a PSBT is finalized and broadcast, the transaction cannot be recalled, so the outputs shown on the signing device are the ones that count.
How it works
BIP-174 defines a binary format that starts with the magic bytes 'psbt' plus 0xFF, followed by a global map and one key-value map for each input and output. It splits the work into roles: a Creator makes the unsigned transaction; an Updater adds the coins being spent, scripts and BIP-32 derivation paths; Signers add signatures using only what the PSBT contains; a Combiner merges copies; a Finalizer builds the final scripts; and an Extractor outputs the finished transaction ready to broadcast.
Source: BIP-174: Partially Signed Bitcoin Transaction Format · checked 4 October 2026
Related words
Educational content, not financial advice. Written by hand and checked against the source named above. Something wrong? Tell us and we reply within two business days.