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  3. The life of a click
  4. · 4 minutes · Pro

Blocked by CORS

Your works in Postman. In the browser: 'blocked by policy'. Your AI has 'fixed' the frontend three times.

This answers: How do I fix 'blocked by CORS policy'? No coding needed. 2 quick decisions.

  • How a request travels
  • Debugging without panic

Checking your access…

How do I fix 'blocked by CORS policy'?

Fix it on the server that answers the request, not in your frontend. Browsers send a OPTIONS request first; the must reply with headers allowing your site's origin and the headers you use. Allow only your own origins rather than everyone, and remember CORS is not authentication.

Trail of the bug
  1. Browser
  2. Your server

Breaks at Browser: Browser blocks it after the preflight

Why AI tools write this bug

AI tools often try to fix from the frontend, which cannot work, or allow every origin with a wildcard to make the error disappear.

How to fix it

  1. Read which origin and which request were blocked.

3 more steps, and a prompt that checks your own app for this bug. Part of Pro.

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Common questions

Why does it work in Postman?
CORS is enforced by browsers. Postman and servers do not apply it.

Related scenarios

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More on this trail

The life of a click: Follow one button press from the browser to the database and back.

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2 decisions, about 4 minutes, and a prompt to check your own app for the same problem.

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How to fix it

  1. Read which origin and which request were blocked.

3 more steps, and a prompt that checks your own app for this bug. Part of Pro.

Unlock