Fix: API CORS Error
Return `Access-Control-Allow-Origin` with the caller's origin
CORS errors are a server response problem, not a client problem. The missing piece is usually `Access-Control-Allow-Origin` (or preflight handling for non-simple requests).
Frequently Asked Questions
What causes API CORS Error?
CORS errors are a server response problem, not a client problem. The missing piece is usually `Access-Control-Allow-Origin` (or preflight handling for non-simple requests).
How to fix API CORS Error?
Confirm the server returns `Access-Control-Allow-Origin` matching the caller. For credentialed requests, use an explicit origin — not `*` — and include `Access-Control-Allow-Credentials: true`.
Example fix from Kintify Fix
Input: Fetch from app.example.com to api.example.com blocked by CORS
Output: Confirm the server returns `Access-Control-Allow-Origin` matching the caller. For credentialed requests, use an explicit origin — not `*` — and include `Access-Control-Allow-Credentials: true`.
Used by developers debugging real production systems