Access to XMLHttpRequest at 'http://dummy.restapiexample.com/api/v1/employees' from origin 'http://127.0.0.1:8000' has been blocked by CORS policy: Request header field x-csrf-token is not allowed by Access-Control-Allow-Headers in preflight response.

Example 1: Access to XMLHttpRequest at 'http://localhost/MySQL_pracs/InsertUser.php' from origin 'http://localhost:4200' has been blocked by CORS policy: Request header field content-type is not allowed by Access-Control-Allow-Headers in preflight response.

//Access to XMLHttpRequest at 'http://localhost/[api path].php' from origin 'http://localhost:4200' has been blocked by CORS policy: Request header field content-type is not allowed by Access-Control-Allow-Headers in preflight response.

//The error is simply saying that "Content-Type" is missing from "Access-Control-Allow-Headers".

//Therefore we need to add "Content-Type" to "Access-Control-Allow-Headers".

<?php 
header('Access-Control-Allow-Headers: Content-Type');
-----
?>

Example 2: Access to XMLHttpRequest at 'https://hddn92.skylinewebcams.com/1071speed-1606566964102.ts' from origin 'https://www.skylinewebcams.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

XMLHttpRequest cannot load http://localhost:9200/_all. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:9100' is therefore not allowed access.