{"glossary_note":"One entry per term. Each entry answers its own address as JSON.","glossary_rules":{"Sources":"Each entry is pinned to primary sources — a specification, an RFC, an EIP, or a party's own published documents — listed on the entry.","Numbers":"Entry text carries links rather than figures. Where a quantity matters, the entry links the source that holds it, so nothing here can go stale in silence.","Named parties":"A party is described as what it is and does, per its own documents. No ranking, no endorsement, and no comparison between parties."},"glossary":[{"slug":"facilitator","title":"facilitator","kind":"term","short":"A facilitator is a service that verifies and settles x402 payments on behalf of a seller. The seller's endpoint quotes a price, the buyer's client signs a payment authorization, and the facilitator checks that authorization against the quote and submits it to the blockchain.","path":"/glossary/facilitator"},{"slug":"payto","title":"payTo","kind":"term","short":"payTo is the field in an x402 payment quote that names the address a payment is sent to. It travels inside the HTTP 402 challenge, so it is chosen by whoever controls the endpoint at the moment of the quote, and it can differ between one request and the next.","path":"/glossary/payto"},{"slug":"catalogue","title":"catalogue","kind":"term","short":"A catalogue is a published list of x402 endpoints that a buyer or an agent can read to discover what is payable. Facilitators operate them, listing the endpoints that settle through the facilitator, so a listing is a curation decision rather than a property of the endpoint itself.","path":"/glossary/catalogue"},{"slug":"verify-and-settle","title":"verify and settle","kind":"term","short":"Verify and settle are the two operations an x402 facilitator exposes. Verify checks a signed payment payload against the quote the endpoint issued; settle submits that payload to the blockchain. They are separate calls, and a payload that passes verification has still moved no money.","path":"/glossary/verify-and-settle"},{"slug":"accepts-array","title":"accepts array","kind":"term","short":"The accepts array is the body of an x402 payment challenge: the list an endpoint returns with HTTP 402 when a request arrives unpaid. Each element of that array is one payment option the endpoint will take, stated in machine-readable terms.","path":"/glossary/accepts-array"},{"slug":"http-402","title":"HTTP 402","kind":"rail","short":"HTTP 402 is the response status code named Payment Required. RFC 9110 reserves it and defines no payment format, which leaves the meaning of such a response to whatever protocol is layered above it. x402 is one such protocol, and the status code is not the same thing as the protocol.","path":"/glossary/http-402"},{"slug":"settlement","title":"settlement","kind":"term","short":"Settlement is the step where an authorised x402 payment is submitted to the blockchain and the transfer actually happens. A quote, a signature and a successful verification all precede it, and none of them is a settlement.","path":"/glossary/settlement"},{"slug":"x402","title":"x402","kind":"rail","short":"x402 is an open protocol for paying for an HTTP request with a stablecoin transfer, using the HTTP 402 status code to carry the terms. It lets a client — often software rather than a person — pay per call, with no account, no key exchange and no subscription.","path":"/glossary/x402"},{"slug":"eip-3009","title":"EIP-3009","kind":"term","short":"EIP-3009 is an Ethereum token standard extension that lets a token holder sign a transfer authorization off-chain, which anyone can then submit on-chain. It is the mechanism under x402's exact scheme: the payer signs, and the facilitator pays the gas to submit.","path":"/glossary/eip-3009"},{"slug":"mpp","title":"MPP","kind":"rail","short":"MPP — the Machine Payments Protocol — is an open protocol for machine-to-machine payments over HTTP, published at mpp.dev. It uses the HTTP 402 status to carry payment terms, and it is a separate specification with its own schemes and its own supported networks.","path":"/glossary/mpp"},{"slug":"coinbase-cdp","title":"Coinbase Developer Platform (CDP)","kind":"player","short":"Coinbase Developer Platform (CDP) is Coinbase's developer product suite. In the x402 ecosystem it operates a facilitator — the service that verifies and settles payments for sellers that configure it — and publishes the discovery catalogue attached to that facilitator, the x402 Bazaar.","path":"/glossary/coinbase-cdp"},{"slug":"x402-foundation","title":"x402 Foundation","kind":"player","short":"The x402 Foundation is the organization that stewards the x402 specification. The protocol's public repository is published under its GitHub organization, which is the source of record for the schemes, the challenge format and the facilitator operations.","path":"/glossary/x402-foundation"},{"slug":"x402-org-facilitator","title":"x402.org facilitator","kind":"player","short":"The x402.org facilitator is the public facilitator served from the protocol's own project site. It verifies and settles payments for sellers that configure it, and it maintains a discovery catalogue of its own, separate from any other facilitator's.","path":"/glossary/x402-org-facilitator"}],"selected":{"slug":"eip-3009","kind":"term","title":"EIP-3009","question":"What is EIP-3009 in x402?","short":"EIP-3009 is an Ethereum token standard extension that lets a token holder sign a transfer authorization off-chain, which anyone can then submit on-chain. It is the mechanism under x402's exact scheme: the payer signs, and the facilitator pays the gas to submit.","mechanism":["The standard defines `transferWithAuthorization`: a signed message naming the sender, the recipient, the value, a validity window and a random nonce. Because the nonce is arbitrary rather than sequential, authorizations can be signed and submitted out of order, and each one can be redeemed a single time.","For a payment made over HTTP this removes the payer's need to hold gas or to broadcast anything at all. The signature travels in the retried request, the [facilitator](/glossary/facilitator) checks it against the quote and submits it, and the token contract enforces the window and the nonce."],"citations":[{"url":"https://eips.ethereum.org/EIPS/eip-3009","publisher":"Ethereum Improvement Proposals","title":"EIP-3009: Transfer With Authorization","read_on":"2026-08-27"},{"url":"https://github.com/x402-foundation/x402","publisher":"x402 Foundation","title":"The x402 specification repository","read_on":"2026-08-27"}],"handoff":{"routes":["/method"],"sentence":"The settle leg probe402 runs, and the network and asset it will accept, are set out in [the method](/method)."},"related":[{"slug":"settlement","title":"settlement","path":"/glossary/settlement"},{"slug":"verify-and-settle","title":"verify and settle","path":"/glossary/verify-and-settle"},{"slug":"x402","title":"x402","path":"/glossary/x402"}],"terms_used":["facilitator"],"last_reviewed":"2026-08-27","review_hash":"fd1f782234585cde","url":"https://probe402.com/glossary/eip-3009"},"requested_entry_problem":null}