x402 SDKs & Libraries

The libraries to add x402 payments to your code — by language. Curated real projects, live GitHub stars.

The x402 flow in one glance

# 1. Client requests a protected resource
GET /api/data            ->   402 Payment Required
                              { amount: "0.01", asset: "USDC", chain: "base", payTo: "0x..." }

# 2. Client pays and retries with proof
GET /api/data
X-PAYMENT: <signed payment payload>   ->   200 OK + data

# A facilitator verifies & settles the payment on-chain.

Quickstart by framework

Add a paywall to a single route. Package APIs evolve — confirm the exact options against the official x402 docs.

Next.js

// npm install @x402/next @x402/core @x402/evm
// middleware.ts
import { paymentMiddleware } from "@x402/next";

export const middleware = paymentMiddleware(
  {
    "/api/data": {
      accepts: [{ amount: "0.01", asset: "USDC", network: "base", payTo: "0xYourAddress" }],
      description: "Premium data endpoint",
    },
  },
  { facilitator: { url: process.env.X402_FACILITATOR_URL } }
);

export const config = { matcher: ["/api/data"] };

Node.js / Express

// npm install express @x402/express @x402/core @x402/evm
import express from "express";
import { paymentMiddleware } from "@x402/express";

const app = express();

app.use(paymentMiddleware({
  "GET /weather": {
    accepts: [{ amount: "0.01", asset: "USDC", network: "base", payTo: "0xYourAddress" }],
    description: "Weather data",
  },
}));

app.get("/weather", (req, res) => res.json({ tempC: 21 }));
app.listen(3000);

Python (Flask)

# pip install x402 flask
from flask import Flask, jsonify
from x402.flask import require_payment

app = Flask(__name__)

@app.get("/data")
@require_payment(amount="0.01", asset="USDC", network="base", pay_to="0xYourAddress")
def data():
    return jsonify({"ok": True})

On the client side, libraries like @x402/fetch wrap your requests so payment + retry happen automatically. Need to settle on-chain yourself? See the facilitator list.

TypeScript / JavaScript

Python

Rust

Go

Frequently asked questions