Basis of Lightning Technology (BOLT)

Basis of Lightning Technology, or BOLT, is the set of open specifications that define how the Lightning Network operates. The documents, numbered BOLT 1 through 11, standardize everything from the peer-to-peer messaging protocol and channel lifecycle to invoice formats and onion routing, so that independent software implementations can interoperate.

Why it matters

Lightning is not a single program but a network of implementations, including LND, Core Lightning, and Eclair, written by different teams in different languages. The BOLTs are what let a node running one implementation open channels and route payments with a node running another, exactly as email standards let different providers exchange mail. Without a common specification, bitcoin's payment layer would have fragmented into incompatible islands controlled by whichever company shipped the dominant app.

How it works

Each BOLT covers one layer of the stack. BOLT 2 specifies how two nodes negotiate, fund, and close a payment channel. BOLT 3 defines the exact bitcoin transaction formats that make channels enforceable on-chain. BOLT 4 describes the Sphinx onion routing that hides a payment's full path from intermediate nodes, BOLT 7 the gossip protocol nodes use to discover the network's channels, and BOLT 11 the familiar lightning invoice format. Changes go through open review among implementers, a slower and less formal process than bitcoin's BIP system but serving the same purpose: no single company owns the protocol, so no single company can change the rules of the money built on it.