How to Check API CORS Headers
TL;DR:
To check API CORS: use /en/cors Enterno.io checker — enter endpoint and origin, get all CORS headers + preflight test. Diagnoses common issues: missing Allow-Origin, wildcard-with-credentials, missing preflight.
Step-by-step guide
- Open CORS checker. Go to /en/cors.
- Enter endpoint URL. Example: https://api.example.com/users. Method: GET/POST/PUT/DELETE.
- Specify Origin. The domain where the fetch originates. Example: https://app.example.com.
- Run the check. The tool performs an OPTIONS preflight + real request and shows every CORS header in the response.
- Read diagnostics. Typical fixes: add
Access-Control-Allow-Origin: https://app.example.com(or whitelist). With credentials — no wildcard allowed.
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Frequently Asked Questions
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