Security
Processed locally in your browser — not uploaded
CORS Header Generator & Simulator
Configure CORS parameters and generate copyable CORS response header snippets for Express.js, NestJS, Nginx, AWS API Gateway, and Apache. Features a live pre-flight OPTIONS simulator to test origin matching. Runs entirely in your browser.
CORS Configuration Parameters
⚡ Live Pre-flight OPTIONS Simulator
✅ PRE-FLIGHT ALLOWED BY CORS POLICY
// Express.js CORS Middleware Setup
const cors = require('cors');
const corsOptions = {
origin: 'https://moayyadfaris.com',
methods: ['GET', 'POST', 'PUT', 'DELETE', 'OPTIONS'],
allowedHeaders: ['Content-Type', 'Authorization', 'X-Requested-With'],
credentials: true,
maxAge: 86400
};
app.use(cors(corsOptions));01
How to use
- Configure allowed origin domains, HTTP methods, and allowed request headers.
- Toggle 'Allow Credentials' if cookies or Authorization headers are sent.
- Select your target framework tab (Express.js, NestJS, Nginx, AWS API Gateway, or Apache).
- Copy ready-to-use backend CORS code snippets directly into your application server.
- Use the built-in Pre-flight OPTIONS Simulator to test origin matching.
02
Understanding the output
The generator creates exact `Access-Control-Allow-Origin`, `Access-Control-Allow-Methods`, `Access-Control-Allow-Headers`, and `Access-Control-Allow-Credentials` headers according to the W3C CORS specification.
03
Common issues & tips
- •You cannot set `Access-Control-Allow-Origin: *` while simultaneously setting `Access-Control-Allow-Credentials: true`. Browsers reject credentialed requests with wildcard origins.
- •Ensure pre-flight `OPTIONS` requests return HTTP 204 or 200 before the actual `POST`/`PUT`/`DELETE` request.
Frequently asked questions
- Can I use wildcard origins with credentials?
- No. Setting Access-Control-Allow-Origin: * with Access-Control-Allow-Credentials: true is explicitly blocked by modern web browsers for security.