Not sure what information is being passed by your web browser to a site you are visiting? This small utility displays all request headers being passed by a web request sent to portchekers.com
|If-Modified-Since||Fri, 14 Dec 2018 12:57:46 UTC|
When you open a page through a browser, typing in the address bar, there is a connection to a remote server, usually to port 80. Such a request is called GET-request - this is one of the main types of HTTP-protocol requests. Sending a request, as well as its contents, usually hidden from users, but there is nothing secret about them.