The only thing I remember about CORS is that it takes way longer than expected to debug, by design the error messages sent to the browser are intentionally gutted, and CORS error scenarios are hard to tell from other failure modes atfirst glance.

Generally when I'm debugging these, I need/want to know what was the preflight (if applicable), and was the preflight what was expected? When I help others debug these, generally I find there is little expectation of what the preflight "should" be, and instead just a bunch of stochastic attempts to adjust the server's response headers to get the browser to capitulate — regardless of whether that makes any sense at all.

I would also say I think Firefox's network inspector is better in this area. (But I'm often having to ask others to "no, don't send the failing request, send the CORS preflight", we need to understand what happened with it.)

> Anecdotally, lots of developers I’ve talked with don’t understand well how CORS works.

Yeah, most FE devs I've worked with seem to not understand CORS.

> Is the CORS API too complex and confusing

I think it can be hard if you don't understand why the exceptions to preflights are what they are, but the moment you internalize "because the browser can already emit that request in other cases" then it becomes obvious what categories are what & why.

Sometimes I'm not even sure what I truly 'understand.' When even senior engineers working on products used by hundreds of millions of people, like Zoom, have had these kinds of issues, it makes me wonder. So I usually just write code the way it was left by my seniors, out of inertia. But I realize that the area I work in is actually incredibly abstracted.

I honestly just can’t be arsed. I write the code to do the thing I want, and if CORS throws a wrench into things, I make Claude fix it for me. I’m tired boss.

It's not just CORS that's hard to understand. Many (most?) developers don't really understand the threat model. And even when it's explained it hard to see why it's a big deal. The article does a nice job giving a concrete example.