Sometimes application requires to get preflight request before sending the target request.
For example before sending this request:
POST /createAdmin
There can be send automatically the following preflight:
OPTIONS /createAdmin
Which tells the browser whether the subsequent request can be sent. Standard GET, HEAD, and POST requests do not trigger a preflight check. However, requests using other HTTP methods, custom headers, or POST requests with nonstandard content types will require a preflight request.