Why is testing CORS in Postman not enough?
Because Postman is not a browser and does not enforce CORS. It cannot confirm your configuration works for the browser. Always test CORS from your actual React app in the browser to confirm it is configured correctly.
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More FAQs in How to Enable CORS on Your Backend API for React Frontends
Use a CORS middleware from your backend framework, allow specific origins instead of a wildcard, handle preflight OPTIONS requests, allow the right methods and headers, and be careful with credentials. Test from the browser, not just Postman.
No. In production, explicitly list the origins that should be allowed, like your frontend domain. A wildcard is a security risk, especially with credentials, because it allows any site to call your API.
For non-simple requests, the browser sends an OPTIONS preflight first. Your server must respond to OPTIONS with the right headers, or the actual request never fires. Using CORS middleware handles this automatically.
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