How can you debug CORS requests using cURL? So far I couldn't find any way to "simulate" the preflight request .
Here's how you can debug CORS requests using curl.
Sending a regular CORS request using cUrl:
curl -H "Origin: http://example.com" --verbose \
https://www.googleapis.com/discovery/v1/apis?fields=
The -H "Origin: http://example.com"
flag is the third party domain making the request. Substitute in whatever your domain is.
The --verbose
flag prints out the entire response so you can see the request and response headers.
The url I'm using above is a sample request to a Google API that supports CORS, but you can substitute in whatever url you are testing.
The response should include the Access-Control-Allow-Origin
header.
Sending a preflight request using cUrl:
curl -H "Origin: http://example.com" \
-H "Access-Control-Request-Method: POST" \
-H "Access-Control-Request-Headers: X-Requested-With" \
-X OPTIONS --verbose \
https://www.googleapis.com/discovery/v1/apis?fields=
This looks similar to the regular CORS request with a few additions:
The -H
flags send additional preflight request headers to the server
The -X OPTIONS
flag indicates that this is an HTTP OPTIONS request.
If the preflight request is successful, the response should include the Access-Control-Allow-Origin
, Access-Control-Allow-Methods
, and Access-Control-Allow-Headers
response headers. If the preflight request was not successful, these headers shouldn't appear, or the HTTP response won't be 200.
You can also specify additional headers, such as User-Agent
, by using the -H
flag.