Fiddler is a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet.

Charles is an HTTP proxy / HTTP monitor / Reverse Proxy that enables a developer to view all of the HTTP and SSL / HTTPS traffic between their machine and the Internet.

Examine, edit, and debug HTML, CSS, and JavaScript on the desktop and on mobile.

HttpFox monitors and analyzes all incoming and outgoing HTTP traffic between the browser and the web servers. It aims to bring the functionality known from tools like HttpWatch or IEInspector to the Firefox browser.

There is no shiny red button on WebScarab, it is a tool primarily designed to be used by people who can write code themselves, or at least have a pretty good understanding of the HTTP protocol.

Monitor all HTTP/HTTPs traffic from your browser. Live HTTP Headers logs all HTTP traffic between Google Chrome and the Internet.

HTTP Debugger Pro - A Professional HTTP Sniffer and Analyzer for Developers

HTTP Headers allows you to quickly see the HTTP header information for the current URL.

BugBattle is the most affordable and fun in-app bug reporting tool for apps & web apps! With BugBattle we put the annoying task of bug fixing upside down and turned it into a fun experience for your whole team.

Working quietly on the Menubar, Surge is a high-performance HTTP/SOCKS5 proxy server.

Monitor and reproduce errors in web sites/applications. Using the built-in recorder feature you’ll know exactly what the user did. This means you don’t have to read call stacks or parse through huge logs to be able to reproduce bugs.

Proxy.app is the perfect tool for debugging and analysing both HTTP requests and responses and modify data in transit.

DebugView is an application that lets you monitor debug output on your local system, or any computer on the network that you can reach via TCP/IP.

Chrome Logger is a Google Chrome extension for debugging server side applications in the Chrome console.

James is a HTTP Proxy and Monitor that enables developers to view and intercept requests made from the browser. It is an open-source alternative to the popular developer tool Charles.

httpreq.com allows you to record and inspect http requests via a unique endpoint. Useful for debugging webhooks, chat-bots and other APIs.

Log and analyze HTTP requests. Makes debugging REST APIs and integrated apps easier.

Rest Client feature rich rest client for developers to debug and test their RESTful web services. It can be used to request a URL using the following HTTP methods: GET, POST, PUT, DELETE, HEAD, PATCH, COPY, SEARCH, OPTIONS.

Omnibug is a plugin for the Google Chrome and Mozilla Firefox browsers to ease developing and debugging web metrics implementations.

intercept.rest is a tool which helps to debug and mock REST APIs Similar to the Network tab in Chrome Dev Tools but works for any API, Mobile apps, webhooks, frontend etc.