title: CORS configuration in AWS API Gateway
body: <p>I am using AWS API Gateway and Lambda Function for one of my applications.</p>
  
  <p>When I send a POST request to API Gateway, it results in an error: </p>
  
  <blockquote>
    <p>'Access-Control-Allow-Origin' header is present on the requested
    resource. Origin '<a href="http://localhost:8888" rel="nofollow noreferrer">http://localhost:8888</a>' is therefore not allowed
    access. The response had HTTP status code 400</p>
  </blockquote>
  
  <p>I enabled CORS in the API Gateway console and added 'Access-Control-Allow-Origin' to "Access-Control-Allow-Headers" and clicked "Enable CORS and replace existing CORS Header" button. It was a success.</p>
  
  <p>But when I reloaded the page, I found 'Access-Control-Allow-Headers' header was not present in "Access-Control-Allow-Headers". </p>
  
  <p>I don't know why AWS is not allowing me to edit "Access-Control-Allow-Headers".</p>