x402

Une application d'exemple illustrant x402 Quicknode pour un accès à une API blockchain en paiement à la requête. Connectez votre portefeuille, authentifiez-vous via SIWE, puis appelez des méthodes RPC/REST sur plusieurs chaînes à l'aide de signatures de paiement EVM.

Auteur

Sergen Uysal

Déployer l'application

Consulter le dépôt

Framework/bibliothèque front-end :

Réagir

Langue :

TypeScript

Outil de compilation/serveur de développement :

Next.js

Présentation générale

This sample app demonstrates Quicknode's x402 protocol for pay-per-request blockchain API access. The x402 protocol enables seamless micropayments for API calls — each request is paid for with an EVM signature, removing the need for traditional API keys or subscription plans.

Connect your wallet, authenticate with Sign-In with Ethereum (SIWE), and request testnet USDC from the faucet. When you execute blockchain methods, if you don't have enough credits, the app will automatically purchase test credits using your testnet USDC. Execute RPC/REST methods across multiple networks including Ethereum, Base Sepolia, Arbitrum, Polygon, and Aptos.

Architecture

Wallet ──► SIWE Auth ──► JWT Token
                            │
                            ▼
              x402 Fetch Wrapper (JWT + EVM payment signature)
                            │
                            ▼
              Quicknode x402 API ──► Blockchain RPC / REST

Each API request is wrapped by @x402/fetch, which automatically signs a payment authorization using your connected wallet. The x402 backend verifies the signature, deducts credits, and proxies the request to the target blockchain network.

Caractéristiques

Wallet Connection via ConnectKit (MetaMask, Coinbase Smart Wallet, etc.)
SIWE Authentication to receive a session JWT
Testnet USDC Faucet on Base Sepolia — credits are automatically purchased with testnet USDC when needed
Multi-Chain RPC/REST Execution across Ethereum, Base Sepolia, Arbitrum, Polygon, and Aptos
Payment Metadata Inspection returned with each response
JSON-RPC, REST, gRPC-Web, and WebSocket method support

Supported Methods

As all JSON-RPC, REST, gRPC-Web, and WebSocket methods are supported, you can call any method available on the target network. For demonstration, the app includes buttons for popular methods:

Method	Protocole	Réseau
`eth_blockNumber`	JSON-RPC	Base Sepolia, Arbitrum, Polygon
`eth_gasPrice`	JSON-RPC	Base
`eth_chainId`	JSON-RPC	Ethereum
Ledger Info	REST	Aptos
Block by Height	REST	Aptos

Conditions préalables

Node.js v18+
pnpm v8+
A browser wallet (e.g., MetaMask) with Base Sepolia testnet configured

Structure du projet

src/
├── app/                  # Next.js App Router (pages & layouts)
├── components/
│   ├── providers.tsx     # Wagmi + React Query + ConnectKit providers
│   └── wallet-connection-shell.tsx
├── hooks/
│   ├── use-x402-auth.ts  # SIWE authentication state
│   ├── use-credits.ts    # Credit balance fetching
│   └── use-x402-fetch.ts # Authenticated fetch wrapper
└── lib/
    ├── constants.ts      # x402 URLs, chain IDs, contract addresses
    ├── methods.ts        # Available RPC/REST method definitions
    ├── types.ts          # TypeScript types
    └── x402.ts           # Core x402 logic (auth, credits, execution)

Environment Variables

Variable	Par défaut	Description
`NEXT_PUBLIC_X402_BASE_URL`	`https://x402.quicknode.com/`	x402 API base URL

Créer un .env.local file to override, but the default points to the public x402 endpoint which you can use for testing without any setup.

NEXT_PUBLIC_X402_BASE_URL=https://x402.quicknode.com/

Pour commencer

1. Clone the repository

git clone https://github.com/quiknode-labs/qn-guide-examples.git
cd qn-guide-examples/sample-dapps/x402-quicknode

2. Install dependencies

pnpm install

3. Start the development server

pnpm dev

Open http://localhost:3000 in your browser. Connect your wallet, authenticate with SIWE, request testnet USDC from the faucet, and start making pay-per-request API calls — credits are automatically purchased with your testnet USDC when needed.