What is an x402 facilitator?

In x402 the server that sells a resource doesn't have to talk to a blockchain. When a client retries with a signed payment, the server can pass it to a facilitator to check it against the scheme and network, then ask the facilitator to submit it and wait for confirmation. The x402 spec says the facilitator generally pays the gas and cannot change the amount or destination, because the client's signature fixes them. Servers can also verify and settle themselves. For the exact scheme with EIP-3009, the client signs an authorisation that names the token, amount, recipient and a validity window; the facilitator submits it with transferWithAuthorization. Because the signature covers the amount and recipient, a changed transfer would not match it and the token contract would refuse it.

If you sell an API over x402, you choose a facilitator that supports the scheme and network you accept. The x402 repository notes that the public x402.org facilitator suits testnet work and recommends choosing a facilitator explicitly for mainnet. Coinbase's developer platform documents a facilitator too. The server still owns the business logic, meaning what to charge and when to hand over the resource; in the x402 flow it verifies the payment, fulfils the request, then settles.

• A facilitator isn't a custodian of the buyer's funds; it executes a transfer the buyer signed.
• It isn't required. Servers may self-facilitate.
• It doesn't decide prices or who may buy; the resource server does.
• A testnet facilitator is not a mainnet one. Check which networks a facilitator supports before you point real payments at it.

• x402 specification and reference implementation (GitHub)
• x402 spec: the exact scheme on EVM
• Coinbase Developer Platform: x402 facilitator

• What is the x402 protocol?x402 uses the HTTP 402 status code so a server can ask for payment and an agent can pay in the same request. How it works and what it needs.
• ACP vs AP2 vs x402 vs MPP: agent payment protocols comparedWhat each agent payment protocol is for: checkout with merchants (ACP), verifiable user mandates (AP2), and pay-per-request machine payments (x402, MPP).

• HTTP 402 Payment Required402 Payment Required is an HTTP response status code that RFC 9110 lists as 'reserved for future use', meaning HTTP itself defines no standard behaviour for it.
• Stablecoin (USDC)A stablecoin is a blockchain token designed to keep a stable value relative to a reference asset, usually a currency such as the US dollar; USDC is a dollar stablecoin issued by Circle.

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