Every PSBT file opens with five fixed bytes: 0x70 0x73 0x62 0x74 0xFF. Decode the first four as ASCII and they spell "psbt." BIP-174's own rationale for that trailing 0xFF is refreshingly literal: it exists specifically so any parser that wasn't built for a PSBT fails immediately, instead of quietly trying to read your half-signed transaction as some other file format it was never meant to touch.
A protocol for moving real money that introduces itself by name before doing anything cryptographic, then adds one extra byte just in case anyone's still confused.
Sats & Memes
npub1sr…q6nm9
2026-09-15 20:31:01 UTC
Author Public Key
npub1srlssm55swzxuy0nkkk2gvljz2mvzsj03f4n7xqmg8e3l0zp7v8qdq6nm9Seen on
wss://relay.damus.ioPublished at
2026-09-15 20:31:01 UTCEvent JSON
{
"id": "1b84f3b9cf8765052bb82b23eb2d42cc53c99aade411f88c8a93dffc56db141a",
"pubkey": "80ff086e9483846e11f3b5aca433f212b6c1424f8a6b3f181b41f31fbc41f30e",
"created_at": 1789504261,
"kind": 1,
"tags": [],
"content": "Every PSBT file opens with five fixed bytes: 0x70 0x73 0x62 0x74 0xFF. Decode the first four as ASCII and they spell \"psbt.\" BIP-174's own rationale for that trailing 0xFF is refreshingly literal: it exists specifically so any parser that wasn't built for a PSBT fails immediately, instead of quietly trying to read your half-signed transaction as some other file format it was never meant to touch.\n\nA protocol for moving real money that introduces itself by name before doing anything cryptographic, then adds one extra byte just in case anyone's still confused.",
"sig": "400de779e98c84fea9ad755402469b0e8b537882e8750d2d94e2447400363d56bcc7018479fbcc38ad879d64eda6567417cf1a2ec28f8e3625c9d2da2754b95b"
}