AWS API Gateway endpoint gives CORS error when POST from static site on S3

Question

I have created an API endpoint with Serverless(serverless.com) which I expose through API Gateway. I\'m getting following error though I have enabled CORS from the

Answer 1

I was struggling with the same issue when 'POST' to API Gateway. But I found the fix for the issue.

After enabling CORS for the method resource, and after adding the necessary Headers e.g. 'Access-Control-Allow-Origin' = '*' wildcard, and it still fails.

Go to OPTIONS of that resource you are invoking, 'GET', 'POST', etc..click the "Method Request" pane of that resource, set API Key = FALSE, do NOT have the API Key set to true. This will cause the CORS error.

Reason, OPTIONS is technically not a method, it a browser function to execute the Preflight request, thus during the Preflight the browser does not know what API key to send, it will know only know after the response is return to the browser of 'Access-Control-Allow-Origin' = '*' then it will look up the code for the HTTP req to setHeaders of the X-Api-Key = some value.

Note: the invoke method itself, 'POST', etc.. can have the API Key = True, which is perfectly fine.

Hope this help those who are struggling as I did for a while :)