Why are 5xx or 4xx Errors Encountered without the \'Access-Control-Allow-Origin\' Header?

5xx or 4xx Error with "No 'Access-Control-Allow-Origin' Header Is Present"

When a browser encounters a 503 error, it indicates a failure on the server side or a lack of server response. Similarly, a 4xx error suggests an issue with the request that hindered server processing.

To investigate, attempt the request using curl or Postman. If a 2xx success response is received, the issue may not lie with the CORS configuration.

However, it's typical for servers to omit the 'Access-Control-Allow-Origin' header in 5xx or 4xx error responses, as they are generally reserved for 2xx and 3xx responses.

Therefore, identifying the cause of the 5xx/4xx error is crucial. Once this error is resolved and a successful response is received, the CORS configuration may be working as intended, eliminating the need for further adjustments.

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