HTTP 402

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

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Next Steps

• How x402 Works — See how HTTP 402 fits into the complete payment flow
• Client & Server — Understand the roles in the x402 protocol
• Quickstart for Sellers — Start implementing HTTP 402 responses