Question 1

What is CORS?

Accepted Answer

CORS (Cross-Origin Resource Sharing) is a browser security mechanism that restricts web pages from making requests to a different domain. Servers must explicitly allow cross-origin requests by including specific HTTP headers like Access-Control-Allow-Origin.

Question 2

How does this CORS Tester work?

Accepted Answer

This tool sends actual HTTP requests from your browser to the URL you specify and inspects the response headers. It checks whether the server includes CORS headers that would allow your browser-based application to access the resource.

Question 3

What does a CORS error mean?

Accepted Answer

A CORS error means the server did not include the necessary Access-Control-Allow-Origin header in its response. This is a server-side restriction — the server needs to be configured to allow cross-origin requests from your domain.

Question 4

What is a preflight request?

Accepted Answer

A preflight request is an OPTIONS request the browser automatically sends before certain cross-origin requests (e.g., POST with custom headers). The server must respond with appropriate CORS headers to allow the actual request to proceed.

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