Header disallowed by preflight response

Query: header disallowed by preflight response

Answer:

When making cross-origin AJAX requests, the browser might send a “preflight” request (OPTIONS method) to check if the actual request (GET, POST, etc.) is allowed by the server. This preflight request includes certain headers such as “Content-Type”. However, sometimes the server’s response indicates that specific headers are not allowed, resulting in the error “header disallowed by preflight response”.

To resolve this issue, you need to ensure that the server allows the headers mentioned in the preflight request. This can be done by configuring the server to include the necessary headers in the response. The server can send the “Access-Control-Allow-Headers” header with a list of allowed headers.

For example, if your preflight request includes the “Content-Type” header, the server response should include the following header:

Access-Control-Allow-Headers: Content-Type

If you have multiple headers, you can separate them with commas:

Access-Control-Allow-Headers: Content-Type, Authorization, X-Another-Custom-Header

By allowing the required headers in the server response, the browser will recognize that the actual request is allowed and will proceed with it.