@aipay/express

AiPay payment middleware for Express — monetize any API with x402 USDC payments.

Install

npm install @aipay/express

Quick Start

import { paymentMiddleware } from "@aipay/express";
import express from "express";

const app = express();

// Protect any route with a paywall
app.use(
  "/api/premium",
  paymentMiddleware({
    endpointId: "ep_xxx", // Your AiPay endpoint ID
    facilitatorUrl: "https://facilitator.aipay.work", // Optional: override facilitator
  })
);

app.get("/api/premium/search", (req, res) => {
  // req.payment contains verified payment info
  res.json({ results: "premium data" });
});

app.listen(3000);

How It Works

1. When a request hits a paid endpoint without a valid X-PAYMENT header, the middleware returns 402 Payment Required with x402 payment requirements.
2. The client pays (USDC on Polygon/Base/Ethereum) and retries with the X-PAYMENT header.
3. The middleware verifies the payment via the facilitator and settles it after a successful response.

API

paymentMiddleware(config)

Returns an Express middleware function.

| Parameter | Type | Description | |---|---|---| | config.endpointId | string | Your AiPay endpoint ID (e.g., ep_xxx) | | config.facilitatorUrl | string? | Override facilitator URL (defaults to https://facilitator.aipay.work) |

License

MIT © AiPay