mitmproxy

mitmproxy is an interactive HTTPS proxy used for debugging, testing, privacy measurements and penetration testing. It intercepts, inspects, modifies and replays web traffic such as HTTP/1, HTTP/2, HTTP/3, WebSockets and other SSL/TLS-protected protocols.

Messages from HTML to Protobuf can be prettified and decoded, specific messages intercepted on the fly and modified before they reach their destination, and requests replayed to a client or server. This makes it useful for exploratory testing of APIs and mobile or web applications, for example to simulate unexpected server responses.

mitmproxy comes as an interactive console interface, a web interface (mitmweb) similar to browser DevTools, and mitmdump for scripting with a Python API. It is free and open source under the MIT licence.