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 Analyzer - HTTP Header Analyzer is an open-source browser extension that allows you to see and analyze the current HTTP request and response header from the website URL.
WebSniffer - WebSniffer is an online tool to outlook HTTP request and response headers.