Miniscript

Miniscript is a structured language that maps a useful subset of Bitcoin Script into composable, analyzable form, letting software reason about spending policies such as which keys, timelocks and combinations can move coins. Developed by Pieter Wuille, Andrew Poelstra and Sanket Kanjalkar, it gained support in Bitcoin Core version 24.0 in 2022.

Why it matters

Raw Bitcoin Script permits complex custody arrangements, but writing it by hand is error-prone, and mistakes have destroyed funds. Miniscript makes constructions such as corporate approval hierarchies and inheritance fallbacks tractable for auditors and interoperable across wallets. Programmable custody is a capability gap between the monetary metals and bitcoin: a gold holder who wants time-delayed or committee-controlled access needs contracts and custodians, while a bitcoin holder can encode those rules into the coins themselves. Miniscript is the tooling that makes doing so safe enough for institutions.

How it works

A wallet author writes a policy, for example two of three keys, or one key after a 90-day timelock. A compiler turns the policy into a miniscript expression, which corresponds directly to concrete Script opcodes. Because miniscript is designed for static analysis, software can compute the maximum transaction size, verify that funds cannot become permanently stuck, and determine exactly which signatures are needed to spend, all before any coins move.