Edge-Computing

A lot of CORS bugs don’t start in the app. They start at the edge. I’ve seen teams spend days debugging “random” frontend failures only to find the real issue sitting in a CDN rule added six months earlier by someone trying to improve cache hit ratio. The app was fine. The browser was fine. The CDN was serving the wrong CORS headers to the wrong origin. That’s the messy reality of global CDN configurations: once responses are cached and reused across regions, CORS mistakes get amplified fast. ...

CORS gets weird at the edge. On a normal app server, you usually control one thing: the response. At the edge, you control the response, the cache key, sometimes the request headers, and sometimes a chain of proxies you barely remember setting up six months ago. That’s where small CORS mistakes turn into “works in curl, fails in browser” bugs. This guide is the version I wish I had the first few times I debugged CORS on a CDN or edge worker. ...