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x402 is the open payment standard that enables services to charge for access to their APIs and content directly over HTTP. It is built around the HTTP 402 Payment Required status code and allows clients to programmatically pay for resources without accounts, sessions, or credential management. With x402, any web service can require payment before serving a response, using crypto-native payments for speed, privacy, and efficiency. Want to contribute to our docs? The GitBook repo is open to PRs! Our only ask is that you keep these docs as a neutral resource, with no branded content other than linking out to other resources where appropriate. Note about the docs: These docs are the credibly neutral source of truth for x402, as x402 is a completely open standard under the Apache-2.0 license. Coinbase Developer Platform is currently sponsoring AI-powered docs for users here, as we migrate to our own AI-powered solution on the main x402.org domain.

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Why Use x402?

x402 addresses key limitations of existing payment systems:
  • High fees and friction with traditional credit cards and fiat payment processors
  • Incompatibility with machine-to-machine payments, such as AI agents
  • Lack of support for micropayments, making it difficult to monetize usage-based services

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Who is x402 for?

  • Sellers: Service providers who want to monetize their APIs or content. x402 enables direct, programmatic payments from clients with minimal setup.
  • Buyers: Human developers and AI agents seeking to access paid services without accounts or manual payment flows.
Both sellers and buyers interact directly through HTTP requests, with payment handled transparently through the protocol.

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What Can You Build?

x402 enables a range of use cases, including:
  • API services paid per request
  • AI agents that autonomously pay for API access
  • Paywalls for digital content
  • Microservices and tooling monetized via microtransactions
  • Proxy services that aggregate and resell API capabilities

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How Does It Work?

At a high level, the flow is simple:
  1. A buyer requests a resource from a server.
  2. If payment is required, the server responds with 402 Payment Required, including payment instructions.
  3. The buyer prepares and submits a payment payload.
  4. The server verifies and settles the payment using an x402 facilitator’s /verify and /settle endpoints.
  5. If payment is valid, the server provides the requested resource.
For more detail, see: The goal is to make programmatic commerce accessible, permissionless, and developer-friendly.

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Get Started

Ready to build? Start here: