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

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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.

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Payment Flow

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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

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Key Components

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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

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Next Steps