For decades, HTTP 402 Payment Required has been reserved for future use. x402 unlocks it, and absolves the internet of its original sin.

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What is HTTP 402?

HTTP 402 is a standard, but rarely used, HTTP response status code indicating that payment is required to access a resource. In x402, this status code is activated to:
  • Inform clients (buyers or agents) that payment is required.
  • Communicate the details of the payment, such as amount, currency, and destination address.
  • Provide the information necessary to complete the payment programmatically.

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Why x402 Uses HTTP 402

The primary purpose of HTTP 402 is to enable frictionless, API-native payments for accessing web resources, especially for:
  • Machine-to-machine (M2M) payments (e.g., AI agents).
  • Pay-per-use models such as API calls or paywalled content.
  • Micropayments without account creation or traditional payment rails.
Using the 402 status code keeps x402 protocol natively web-compatible and easy to integrate into any HTTP-based service.

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Summary

HTTP 402 is the foundation of the x402 protocol, enabling services to declare payment requirements directly within HTTP responses. It:
  • Signals payment is required
  • Communicates necessary payment details
  • Integrates seamlessly with standard HTTP workflows