BOLT
Also: Basis of Lightning Technology
lightning · intermediate
The Lightning Network's specification documents. Like BIPs are to Bitcoin, BOLTs are to Lightning.
BOLTs are numbered specs maintained at github.com/lightning/bolts. They define wire formats, channel state machines, onion routing, gossip propagation, and invoice formats. Any Lightning implementation that claims to interoperate must comply with the BOLTs.
Key ones to know: BOLT-2 (channel state machine), BOLT-4 (onion routing), BOLT-7 (gossip), BOLT-11 (invoices — the lnbc... strings), and BOLT-12 (offers, the static-invoice replacement). BOLT-12 in particular is a significant 2023–2025 milestone: it makes Lightning addresses portable and recurring payments practical.
The three major node implementations — LND, Core Lightning, Eclair — coexist because they all implement the BOLTs. When you point a wallet at a node, it doesn't care which implementation you're running; it cares that the BOLT-11 invoice and BOLT-4 onion are correctly formed.