fastify

@x402/fastify

Fastify middleware integration for the x402 Payment Protocol. This package provides payment middleware for adding x402 payment requirements to your Fastify applications.

Installation

pnpm install @x402/fastify

Quick Start

import Fastify from "fastify";
import { paymentMiddleware, x402ResourceServer } from "@x402/fastify";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";

const app = Fastify();

const facilitatorClient = new HTTPFacilitatorClient({ url: "https://facilitator.x402.org" });
const resourceServer = new x402ResourceServer(facilitatorClient)
  .register("eip155:84532", new ExactEvmScheme());

// Apply the payment middleware with your configuration
paymentMiddleware(
  app,
  {
    "GET /protected-route": {
      accepts: {
        scheme: "exact",
        price: "$0.10",
        network: "eip155:84532",
        payTo: "0xYourAddress",
      },
      description: "Access to premium content",
    },
  },
  resourceServer,
);

// Implement your protected route
app.get("/protected-route", async () => {
  return { message: "This content is behind a paywall" };
});

app.listen({ port: 3000 });

Configuration

The paymentMiddleware function accepts the following parameters:

paymentMiddleware(
  app: FastifyInstance,
  routes: RoutesConfig,
  server: x402ResourceServer,
  paywallConfig?: PaywallConfig,
  paywall?: PaywallProvider,
  syncFacilitatorOnStart?: boolean
)

Parameters

1. app (required): The Fastify instance to register hooks on
2. routes (required): Route configurations for protected endpoints
3. server (required): Pre-configured x402ResourceServer instance
4. paywallConfig (optional): Configuration for the built-in paywall UI
5. paywall (optional): Custom paywall provider
6. syncFacilitatorOnStart (optional): Whether to sync with facilitator on startup (defaults to true)

API Reference

FastifyAdapter

The FastifyAdapter class implements the HTTPAdapter interface from @x402/core, providing Fastify-specific request handling:

class FastifyAdapter implements HTTPAdapter {
  getHeader(name: string): string | undefined;
  getMethod(): string;
  getPath(): string;
  getUrl(): string;
  getAcceptHeader(): string;
  getUserAgent(): string;
}

Middleware Function

function paymentMiddleware(
  app: FastifyInstance,
  routes: RoutesConfig,
  server: x402ResourceServer,
  paywallConfig?: PaywallConfig,
  paywall?: PaywallProvider,
  syncFacilitatorOnStart?: boolean,
): void;

Registers Fastify hooks (onRequest and onSend) that:

1. Use the provided x402ResourceServer for payment processing
2. Check if the incoming request matches a protected route
3. Validate payment headers if required
4. Return payment instructions (402 status) if payment is missing or invalid
5. Process the request if payment is valid
6. Handle settlement after successful response

Route Configuration

Routes are passed as the second parameter to paymentMiddleware:

const routes: RoutesConfig = {
  "GET /api/protected": {
    accepts: {
      scheme: "exact",
      price: "$0.10",
      network: "eip155:84532",
      payTo: "0xYourAddress",
      maxTimeoutSeconds: 60,
    },
    description: "Premium API access",
  },
};

paymentMiddleware(app, routes, resourceServer);

Paywall Configuration

The middleware automatically displays a paywall UI when browsers request protected endpoints.

Option 1: Full Paywall UI (Recommended)

Install the optional @x402/paywall package for a complete wallet connection and payment UI:

pnpm add @x402/paywall

Then configure it:

const paywallConfig: PaywallConfig = {
  appName: "Your App Name",
  appLogo: "/path/to/logo.svg",
  testnet: true,
};

paymentMiddleware(app, routes, resourceServer, paywallConfig);

Option 2: Basic Paywall (No Installation)

Without @x402/paywall installed, the middleware returns a basic HTML page with payment instructions.

Option 3: Custom Paywall Provider

Provide your own paywall provider:

paymentMiddleware(app, routes, resourceServer, paywallConfig, customPaywallProvider);

Advanced Usage

Multiple Protected Routes

paymentMiddleware(
  app,
  {
    "GET /api/premium/*": {
      accepts: {
        scheme: "exact",
        price: "$1.00",
        network: "eip155:8453",
        payTo: "0xYourAddress",
      },
      description: "Premium API access",
    },
    "GET /api/data": {
      accepts: {
        scheme: "exact",
        price: "$0.50",
        network: "eip155:84532",
        payTo: "0xYourAddress",
        maxTimeoutSeconds: 120,
      },
      description: "Data endpoint access",
    },
  },
  resourceServer,
);

Multiple Payment Networks

paymentMiddleware(
  app,
  {
    "GET /weather": {
      accepts: [
        {
          scheme: "exact",
          price: "$0.001",
          network: "eip155:84532",
          payTo: evmAddress,
        },
        {
          scheme: "exact",
          price: "$0.001",
          network: "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",
          payTo: svmAddress,
        },
      ],
      description: "Weather data",
      mimeType: "application/json",
    },
  },
  new x402ResourceServer(facilitatorClient)
    .register("eip155:84532", new ExactEvmScheme())
    .register("solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", new ExactSvmScheme()),
);

Custom Facilitator Client

If you need to use a custom facilitator server, configure it when creating the x402ResourceServer:

import { HTTPFacilitatorClient } from "@x402/core/server";
import { x402ResourceServer } from "@x402/fastify";
import { ExactEvmScheme } from "@x402/evm/exact/server";

const customFacilitator = new HTTPFacilitatorClient({
  url: "https://your-facilitator.com",
  createAuthHeaders: async () => ({
    verify: { Authorization: "Bearer your-token" },
    settle: { Authorization: "Bearer your-token" },
  }),
});

const resourceServer = new x402ResourceServer(customFacilitator)
  .register("eip155:84532", new ExactEvmScheme());

paymentMiddleware(app, routes, resourceServer, paywallConfig);