CORS Explained: The Complete Guide (with Cheat Sheet)

<p>CORS is one of those things every web developer runs into sooner or later. Most of us know how to fix it — add a header, change a config, ask the backend person to "do

<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>You click "Sign in with Google" on some app you've never used before. A popup flashes, you pick your account, and three seconds later the app knows your name and email. You