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How do you handle CORS (Cross-Origin Resource Sharing) in Node.js?

Q: How do you handle CORS (Cross-Origin Resource Sharing) in Node.js?

**TL;DR.** **CORS** is a browser security mechanism: the browser blocks cross-origin requests unless the server returns the right Access-Control-Allow-* headers. In Node you set those headers — usually via the cors middleware in Express — to **allowlist** specific origins, methods, headers, and credentials. browser origin A OPTIONS preflight Allow-Origin: A <rect

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corssecurityexpress.jsweb development

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Allowlist origins with the cors middleware

import cors from 'cors';

app.use(cors({
  origin: ['https://app.example.com', 'https://admin.example.com'],
  methods: ['GET', 'POST'],
  credentials: true,          // allow cookies
}));
// Manually, you'd set res.setHeader('Access-Control-Allow-Origin', origin) etc.

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