21 BTCx402
x402 is an open payment standard started by Coinbase and now run by the x402 Foundation. Like L402 it uses HTTP 402, but it mostly settles in USDC stablecoins on chains such as Base and Solana rather than in bitcoin.
How it works
The server replies 402 with a PAYMENT-REQUIRED header listing accepted networks and amounts. The client signs a transfer and resends the request with a PAYMENT-SIGNATURE header; a facilitator verifies and settles it on-chain, and the server returns the resource.
x402 vs L402
Both put payment inside HTTP for AI agents. x402 gives agents dollar prices and needs no Lightning channels, but USDC can be frozen by its issuer and the money is not bitcoin. L402 settles in bitcoin over Lightning in about a second, down to millisatoshis, with no issuer.
See also
- L402L402 is a protocol for paying for web resources with Lightning inside an ordinary HTTP request. The server replies 402 "Payment Required" with an invoice and a token; the client pays, retries with the proof and gets access. It needs no account or API key, which suits software agents.
- AI agents and BitcoinAI agents are programs that do work on their own and increasingly need to pay for it: an API call, a page of data, a minute of compute. They cannot open a bank account, but they can hold a Bitcoin key and pay over Lightning in amounts far smaller than a card can handle. That is the case for why the next billion Bitcoin users may not be people. It is a strong argument with real caveats.
- Lightning NetworkLightning is a payment network built on top of Bitcoin. Two parties lock bitcoin in a shared channel and then pay each other instantly and cheaply off-chain; payments can hop across channels to reach anyone.
References
- x402.org x402.org
- x402 (GitHub, x402 Foundation) github.com