CORS Preflight Simulator

Method, Content-Type, and headers, checked against the actual Fetch spec's CORS-safelisted request rules - not an approximation.

Method

Content-Type

Custom headers (comma-separated)

Triggers a preflight OPTIONS request

Content-Type "application/json" isn't one of the three safelisted values (application/x-www-form-urlencoded, multipart/form-data, text/plain).
Header not safelisted: authorization (e.g. Authorization always triggers a preflight).

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