Write, route, cache, and debug Netlify Edge Functions, the Deno-based TypeScript or JavaScript handlers in netlify/edge-functions that run at the network edge in front of static files and serverless functions. Activate this skill whenever someone wants to add auth middleware or a login gate, redirect or rewrite visitors by country or cookie, localize or personalize a page with geolocation, run A/B testing, transform or inject HTML into a response, stream server-side rendering at the edge, or cache an edge response. Also use it when an edge function silently does nothing, runs in the wrong order, ignores its Cache-Control headers, or cannot read an environment variable.