Creating x402 Payment-Protected Servers

Build TypeScript servers that gate API endpoints behind Algorand (AVM) payments using Express.js or Hono middleware.

Prerequisites

Before creating a payment-protected server:

1. Node.js 18+ installed
2. An Algorand address to receive payments (58-character address)
3. A facilitator -- either run your own or use https://facilitator.goplausible.xyz
4. TypeScript project initialized with tsconfig.json

Core Workflow: Middleware-Based Payment Gating

The server middleware intercepts requests to protected routes, checks for a valid X-PAYMENT header, and either returns 402 (pay first) or passes through to the route handler (payment verified).