Reference

What is x402?

x402 is an open standard for internet-native payments over HTTP. It brings back the original intent of the HTTP 402 Payment Required status code, enabling any HTTP resource to require a micro-payment before delivering its response.

The protocol is designed to be stateless and works for both traditional applications and autonomous AI agents. The payment flow follows six steps:

1. The client requests a paid resource.

2. The server responds with 402 Payment Required and a PaymentRequirements object describing the accepted network, scheme, asset, and amount.

3. The client builds a signed PaymentPayload and replays the request with a PAYMENT-SIGNATURE header.

4. The server forwards the payload to a facilitator for verification and settlement.

5. The facilitator validates the payload and submits the payment on-chain.

6. The server delivers the protected resource upon confirmation.

What is a facilitator?

A facilitator is a service that handles the verification and on-chain settlement of x402 payments on behalf of resource servers. It operates as an independent layer between clients, resource servers, and blockchain networks.

The facilitator's three core responsibilities are:

• Verification — Confirms that a client's signed payment payload satisfies the server's declared payment requirements without yet submitting anything on-chain.

• Settlement — Validates the payload and then submits the payment transaction to the blockchain, monitoring it until confirmation.

• Abstraction — Allows resource servers to accept blockchain payments without maintaining direct node connectivity or building their own verification logic.

The facilitator does not hold funds or act as a custodian. It only executes on-chain transactions based on signed payment authorizations provided by clients.

CSPR.cloud x402 Facilitator

CSPR.cloud provides an x402 facilitator for the Casper Network. It supports the exact payment scheme using CEP-18 tokens authorized via EIP-712 typed-data signatures.

Endpoints

URL	Network
https://x402-facilitator.cspr.cloud	Mainnet and Testnet

All endpoints require authorization. Learn how to obtain an access token here.

Supported networks and schemes

The CSPR.cloud facilitator supports the exact scheme on Casper networks:

Network identifier	Description
casper:casper	Casper Mainnet
casper:casper-test	Casper Testnet

Network identifiers follow the CAIP-2 format.

API endpoints

The facilitator exposes three endpoints:

Endpoint	Method	Description
/supported	GET	Returns supported payment schemes and networks
/verify	POST	Validates a payment payload without submitting it on-chain
/settle	POST	Validates a payment payload and settles it on the Casper Network

Examples

The github.com/make-software/casper-x402 repository contains end-to-end examples to build a complete x402 payment flow.