What's actually going on with CORS, under the hood

<p>Your <code>fetch</code> call is correct. The server received it, ran the handler, and sent back a <code>200</code> with a body. Your JavaScript never sees any of that — instead

<h2> TL;DR </h2> <ul> <li>The bug is usually the <strong>preflight</strong> (<code>OPTIONS</code>), not your <code>fetch</code> call or the client library.</li> <li>

<p><em>The CORS error that kills every developer’s first API integration — and the serverless proxy pattern that solves it permanently.</em></p> <p>If you’ve ever built something

<p>If your API has no rate limiting, any client can send as many requests as it wants. A broken retry loop, a scraper, or a user who refreshes too fast all of it hits your server