A crash course in Next.js middleware

Next.js middleware is a powerful feature that runs code before request completion and modifies responses. Introduced in version 12, it can now respond directly to requests without route handlers, improving performance and security. It works with Edge Functions for network edge code execution. Middleware is useful for authentication, authorization, caching, geolocation, A/B testing, and rate limiting. While flexible, developers should consider potential trade-offs like added complexity and latency.