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Fixing CORS errors: a checklist that actually works
Step through origins, preflight failures, and response headers using DevTools before changing architecture.
1 min read
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Start with the Network panel
Identify whether the failing call is the preflight OPTIONS or the actual GET/POST. Different fixes apply to each.
Confirm the request URL, method, and headers your frontend sends—mismatches with server allowlists are a common cause.
When to use a proxy
If you cannot change the third-party API, a server-side proxy or a dedicated CORS proxy with strict allowlists can centralize policy.
Never disable CORS in the browser via extensions in production; fix configuration instead.