Taproot

Before Taproot, spending from a complicated setup — say a 3-of-5 multisig with a time lock — meant revealing the whole script on-chain, so everyone could see the rules. Taproot uses Merkleized Abstract Syntax Trees (MAST): only the branch actually used gets published, and in the happy path everything looks like a plain single-signature payment. Multisig wallets suddenly become indistinguishable from ordinary ones.

Paired with Schnorr signatures, Taproot also lets one signature stand in for many, cutting fees on complex spends and making cooperative closures of Lightning channels cheaper. It activated at block 709,632 on 14 November 2021 after years of mailing-list debate. New Taproot addresses start with bc1p instead of bc1q, and you can spot them in the latest blocks on this block explorer.