BIP 321 — URI Scheme, Matt Corallo

BIP 321 (URI Scheme, Matt Corallo) updates and replaces BIP 21, modernizing the 'bitcoin:' URI format — including handling of multiple payment instructions (such as different address types or Lightning offers) within a single URI so a payer's wallet can select the best mutually supported option. Repository status: Complete.

Debate relevance: Relevant when debating payment UX unification across on-chain and Lightning, and when someone asks what replaced BIP 21. Common misstatements: Assuming Complete means universally adopted — Complete indicates the specification is finished; wallet support is a separate, ongoing question.