Developer & Data

CORS Headers Explainer

Configure and visualize CORS headers — see the preflight request and response.

Runs in your browser

CORS configuration

Client origin (requesting app)Allowed origin (server response)Allowed methodsAllowed headersAllow credentials (cookies, auth)

Server headers

Preflight request

OPTIONS /api/data HTTP/1.1
Host: api.example.com
Origin: https://myapp.com
Access-Control-Request-Method: POST
Access-Control-Request-Headers: Content-Type, Authorization

Server response

Access-Control-Allow-Origin: *

Any origin can access this resource

Access-Control-Allow-Methods: GET, POST, PUT, DELETE

Allowed HTTP methods: GET, POST, PUT, DELETE

Access-Control-Allow-Headers: Content-Type, Authorization

Client may send these custom headers: Content-Type, Authorization

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Stored locally in your browser only — not sent anywhere.

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