How to get Request Headers from xhr request's.

[mavotof]

Hello, reading documentation iv only found how to get response headers from requests.
I need to get request headers from XHR requests that are made naturally when visiting a website and doing tasks, like login (POST requests). Is there a way to interact with the XHR? How can i possibly get request headers, or even possibly save the whole request URL, headers cookies and content, to a text file? I do not mean setting custom headers for requests.

Also lastly, is there a way to cancel a request from reaching server?

Thanks guys!