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@sei-js/x402-next

Next.js middleware integration for the x402 Payment Protocol. This package allows you to easily add paywall functionality to your Next.js applications using the x402 protocol.

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Installation

npm install @sei-js/x402-next

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Quick Start

Create a middleware file in your Next.js project (e.g., middleware.ts): 
import { paymentMiddleware } from '@sei-js/x402-next';

export const middleware = paymentMiddleware(
  "0xYourAddress",
  {
    '/protected': {
      price: '$0.01',
      network: "sei",
      config: {
        description: 'Access to protected content'
      }
    },
  }
);

// Configure which paths the middleware should run on
export const config = {
  matcher: [
    '/protected/:path*',
  ]
};

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Configuration

The paymentMiddleware function accepts three parameters:
  1. payTo: Your receiving address (0x${string})
  2. routes: Route configurations for protected endpoints
  3. facilitator: (Optional) Configuration for the x402 facilitator service
  4. paywall: (Optional) Configuration for the built-in paywall
See the Middleware Options section below for detailed configuration options.

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Middleware Options

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Route Configuration

type RoutesConfig = Record<string, Price | RouteConfig>;

interface RouteConfig {
  price: Price;           // Price in USD or token amount
  network: Network;       // "sei" or "seiTestnet"
  config?: PaymentMiddlewareConfig;
}

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Payment Configuration

interface PaymentMiddlewareConfig {
  description?: string;               // Description of the payment
  mimeType?: string;                  // MIME type of the resource
  maxTimeoutSeconds?: number;         // Maximum time for payment (default: 60)
  outputSchema?: Record<string, any>; // JSON schema for the response
  customPaywallHtml?: string;         // Custom HTML for the paywall
  resource?: string;                  // Resource URL (defaults to request URL)
}

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Example with API Routes

Create protected API routes in your Next.js application: 
// middleware.ts
import { paymentMiddleware } from '@sei-js/x402-next';
import { facilitator } from '@sei-js/x402';

export const middleware = paymentMiddleware(
  "0xYourAddress",
  {
    '/api/premium': {
      price: '$0.05',
      network: "sei",
      config: {
        description: 'Premium API access',
        maxTimeoutSeconds: 120,
      }
    },
    '/api/data-feed': {
      price: '$0.01',
      network: "sei",
      config: {
        description: 'Real-time data feed',
        mimeType: 'application/json',
      }
    }
  },
  facilitator,
  {
    appName: 'My Next.js App',
    appLogo: '/logo.png'
  }
);

export const config = {
  matcher: [
    '/api/premium/:path*',
    '/api/data-feed/:path*',
  ]
};

// pages/api/premium/index.ts or app/api/premium/route.ts
export async function GET() {
  return Response.json({
    message: "This is premium content",
    data: {
      timestamp: new Date().toISOString(),
      premium: true
    }
  });
}

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App Router Support

The middleware works with both Pages Router and App Router:

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App Router (app directory)

// middleware.ts
import { paymentMiddleware } from '@sei-js/x402-next';

export const middleware = paymentMiddleware(
  "0xYourAddress",
  {
    '/dashboard': {
      price: '$0.10',
      network: "sei",
      config: {
        description: 'Premium dashboard access'
      }
    }
  }
);

export const config = {
  matcher: ['/dashboard/:path*']
};

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Pages Router (pages directory)

// middleware.ts
import { paymentMiddleware } from '@sei-js/x402-next';

export const middleware = paymentMiddleware(
  "0xYourAddress",
  {
    '/premium': {
      price: '$0.05',
      network: "sei",
      config: {
        description: 'Premium page access'
      }
    }
  }
);

export const config = {
  matcher: ['/premium/:path*']
};

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Deployment Considerations

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Vercel

The middleware works seamlessly with Vercel’s Edge Runtime: 
// middleware.ts
export const config = {
  matcher: [
    '/api/premium/:path*',
    '/protected/:path*'
  ],
  runtime: 'edge' // Optional: explicitly use Edge Runtime
};

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Other Platforms

The middleware is compatible with any platform that supports Next.js middleware:
  • Netlify
  • AWS Amplify
  • Railway
  • Self-hosted deployments