Charles is an HTTP proxy / HTTP monitor / Reverse Proxy that enables a developer to view all of the HTTP and SSL / HTTPS traffic. Developed by Karl von Randow
License: Commercial
Zed Attack Proxy (ZAP) is primarily aimed at security testing with strong automated scanning capabilities, whereas Charles is focused on web debugging and performance testing with robust data visualization. ZAP is open-source and free, while Charles is a commercial product, offering different strengths depending on the user's needs.