HTTP-TRACKER - HTTP-TRACKER is an advanced browser extension that allows you to examine HTTP request headers, cookies, response Headers, website data, cookies and modify request headers before sending them.
Google Chrome Developer Tools - Get started with Google Chrome's built-in web developer tools.
Sky Live HTTP Headers - Sky Live HTTP Headers is an open-source browser extension that visually displays HTTP requests and response headers from every website you visit.
Firefox Developer Tools - Examine, edit, and debug HTML, CSS, and JavaScript on the desktop and on mobile.
HTTP Header Spy - HTTP Header Spy is a browser extension that allows you to inspect the request and response header of any website URL.
Modify Header Value (HTTP Headers) - Modify Header Value (HTTP Headers) is a browser extension that allows you to add, modify or remove a header for any request to your preferred domains.