What is x402?
x402 is an open payment protocol that brings stablecoin payments to plain HTTP. It revives theHTTP 402 Payment Required status so that servers can charge for APIs and digital content seamlessly.
Clients (human users or AI agents) can pay programmatically to access resources
without creating a separate account with every service. Merchant facilitator
credentials are a different layer: PayAI requires them for
batch settlement and paid facilitator usage.
Learn more about the x402 project at x402.org.
Why x402?
Legacy payment rails weren’t built for the web’s speed or for machine-to-machine use. They are slow, costly, and require sign-ups and keys. x402 embeds payment into the web’s native request–response flow, enabling instant, global, usage-based payments with minimal integration—ideal for humans and autonomous agents alike.Benefits
- Simple HTTP integration using status code 402
- Pay-per-request and other usage-based pricing
- Micropayments with stablecoins (e.g., USDC on Solana)
- Agent-native: AI agents can discover and pay automatically
- Payment-based access without a separate customer subscription; applications may still require identity or other access controls
How it works (high level)
- A buyer (client) requests a resource from a seller (server).
- If payment is required, the seller responds with 402 and payment instructions.
- The buyer constructs and sends a payment payload.
- The seller verifies and settles the payment (often via a facilitator) and then returns the resource.
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