Glossary
L402
A Lightning-Labs protocol that pairs HTTP 402 Payment Required with Lightning Network invoices, enabling sub-cent metered payments for APIs and content.
The Lightning-native predecessor of x402. A server returns HTTP 402
with a macaroon credential and a Lightning invoice in the headers; the
client pays the invoice, presents the now-signed macaroon, and the
server grants access. Pricing per request can be fractions of a cent
because Lightning settles off-chain.
L402 originated at Lightning Labs in 2020 as “LSAT,” and was renamed to L402 in the 2022-2023 window. It saw real use for paid API gateways in the Bitcoin and Lightning ecosystems but never broke out into the broader web.
The protocol assumes a counterparty already in a Lightning-capable state, which limits the addressable population. x402protocolsAn open protocol revived by Coinbase in 2025 that uses the long-reserved HTTP 402 "Payment Required" status to let agents and APIs settle micropayments, including in stablecoins. Open full entry reuses the HTTP 402 framing but stays rail-agnostic, betting on stablecoins as the common settlement layer. The two protocols cover overlapping ground; which becomes the convention is unsettled.