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Monetize your API with x402

x402 lets you monetize HTTP APIs and content with on-chain payments, while keeping your existing server stack. Benefits: ✅ Customers don’t pay network fees.
✅ Payment settles in < 1 second.
✅ Universal compatibility — if it speaks HTTP, it speaks x402.

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Architecture at a glance

x402 sequence diagram
  • Client: Calls your protected resource and submits payments.
  • Server (merchant): Advertises payment requirements, verifies payments, fulfills requests, and settles payments.
  • Facilitator: Verifies and/or settles payments on your behalf via standard endpoints.
  • Blockchain: Where payments are executed and confirmed.

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It’s that easy

Add x402 payments to your server with just a few lines: 
import { paymentMiddleware, x402ResourceServer } from "@x402/express";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";
import { facilitator } from "@payai/facilitator";

const facilitatorClient = new HTTPFacilitatorClient(facilitator);

app.use(
  paymentMiddleware(
    {
      "GET /weather": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.001",
            network: "eip155:84532",
            payTo: evmAddress,
          },
        ],
        description: "Weather data",
        mimeType: "application/json",
      },
    },
    new x402ResourceServer(facilitatorClient)
      .register("eip155:84532", new ExactEvmScheme()),
  ),
);

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Getting started

Select one of the quickstart examples, or read the reference for more details.

Express

Quickstart for building an x402-enabled server with Express.

Hono

Quickstart for building an x402-enabled server with Hono.

Next.js

Quickstart for building an x402-enabled server with Next.js.

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Facilitator setup

The @payai/facilitator package provides a pre-configured facilitator that connects to the PayAI facilitator at https://facilitator.payai.network: 
npm install @payai/facilitator

import { facilitator } from "@payai/facilitator";
import { HTTPFacilitatorClient } from "@x402/core/server";

const facilitatorClient = new HTTPFacilitatorClient(facilitator);
This works immediately on the free tier. For production, set PAYAI_API_KEY_ID and PAYAI_API_KEY_SECRET environment variables — see Going to Production. For details on how authentication works or to implement it without PayAI packages, see Facilitator Authentication.

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x402 reference

For a deeper dive into message shapes, headers, verification and settlement responses, see the x402 Reference.

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