What is x402?

1.What is x402?

HTTP has reserved status code 402, Payment Required, for decades without a common way to use it. x402 defines that way: the server says what payment it needs, the client pays, and the request is retried with proof of payment. It is aimed at pay-per-request APIs and content that agents buy on demand.

2.How does the payment flow work?

1. An agent sends an HTTP request and receives a 402 response.
2. The agent pays instantly with stablecoins.
3. Access to the API or resource is granted, with no key management.

HTTP/1.1 402 Payment Required
Content-Type: application/json

The payment requirements and the proof the client returns are defined by the x402 specification; use its documentation for field names.

x402 supports all EVM-compatible chains, Solana and more, according to x402.org.

3.When does x402 fit, and when does it not?

• Fits: per-call APIs, datasets, or content that an agent should be able to buy without a human creating an account.
• Does not fit: most subscription SaaS checkouts, where the buyer is a company, pays by invoice or card, and needs a contract. Those flows need readable pricing and a checkout an agent can follow, and commerce protocols such as ACP and UCP are aimed at that case.
• Not the same as Cloudflare's Pay per crawl, which lets AI crawlers pay per page and is in private beta.

4.How do you check it?

1. Request a paid endpoint without payment and confirm a 402 response with machine-readable payment requirements.
2. Complete a test payment on a test network and confirm the retried request succeeds.
3. Readiness scanners check the payments layer: ora.ai Scan's payments layer has 6 checks worth 10 of 100 points; Cloudflare Is It Agent Ready lists x402, MPP, UCP and ACP.

5.Where does it sit in the readiness stack?

Layer 4, Pay.

Frequently asked questions