The most important tool for testing web applications is the HTTP Proxy. This tool allows you to intercept all the communication between the browser and the server in both directions. These proxies are called man-in-the-middle proxies. These tools will let us understand how an application works, and most importantly, it will allow us to intercept the requests, responses, and modify them.

Usually, the proxy will run in the same machine as the browser you're using for testing the application. The most used HTTP proxies by security professionals are Burp Suite from PortSwigger security (https://portswigger.net/burp/proxy.html) and Zed Attack Proxy (ZAP) (https://www.owasp.org/index.php/OWASP_Zed_Attack_Proxy_Project). We also have the MITM proxy. It is a newer alternative developed in Python and is good to build tools or automate certain scenarios. The downside is that it's the only console, and there is no GUI, which for our purposes, is a benefit.