How x402 Works

This page explains the complete payment flow in x402, from initial request to payment settlement.

Overview

x402 enables programmatic payments over HTTP using a simple request-response flow. When a client requests a paid resource, the server responds with payment requirements, the client submits payment, and the server delivers the resource.

Payment Flow

Step-by-Step Process

1. Client makes HTTP request - The client sends a standard HTTP request to a resource server for a protected endpoint.

2. Server responds with 402 - The resource server returns an HTTP 402 Payment Required status code with payment details in the response body.

3. Client creates payment - The client examines the payment requirements and creates a payment payload using their wallet based on the specified scheme.

4. Client resubmits with payment - The client sends the same HTTP request again, this time including the X-PAYMENT header containing the signed payment payload.

5. Server verifies payment - The resource server validates the payment payload either:

   • Locally (if running their own verification)
   • Via a facilitator service (recommended)

6. Facilitator validates - If using a facilitator, it checks the payment against the scheme and network requirements, returning a verification response.

7. Server processes request - If payment is valid, the server fulfills the original request. If invalid, it returns another 402 response.

8. Payment settlement - The server initiates blockchain settlement either:

   • Directly by submitting to the blockchain
   • Through the facilitator’s /settle endpoint

9. Facilitator submits onchain - The facilitator broadcasts the transaction to the blockchain based on the payment’s network and waits for confirmation.

10. Settlement confirmation - Once confirmed onchain, the facilitator returns a payment execution response.

11. Server delivers resource - The server returns a 200 OK response with:

    • The requested resource in the response body
    • An X-PAYMENT-RESPONSE header containing the settlement details

Key Components

• Client & Server - The roles and responsibilities of each party
• Facilitator - Optional service that handles payment verification and settlement
• HTTP 402 - How payment requirements are communicated
• Networks & Facilitators - Available networks and facilitator options

Why This Design?

The x402 protocol is designed to be:

• Stateless - No sessions or authentication required
• HTTP-native - Works with existing web infrastructure
• Blockchain-agnostic - Supports multiple networks through facilitators
• Developer-friendly - Simple integration with standard HTTP libraries

Next Steps

• Ready to accept payments? See Quickstart for Sellers
• Want to make payments? See Quickstart for Buyers
• Looking for specific networks? Check Network Support