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.

Surge for Mac - Advanced Web Debugging Proxy for Mac & iOS

Live HTTP Headers - The goal of this project is to adds information about the HTTP headers in three ways:

Weer - A HTTP protocol debugger with Chrome DevTools frontend interface

WebSniffer - WebSniffer is an online tool to outlook HTTP request and response headers.

Cellist - Cellist is an all-in-one HTTP debugging proxy software designed for OS that provides a straightforward approach to put a proxy between the HTTP client and the internet.