Open-Source Alternatives to Fiddler

Betwixt is a system-wide network monitor and web debugging proxy that captures network requests from any installed application. It functions as an HTTPS traffic inspector, routing operating system and command line interface traffic through a local proxy for analysis. The tool utilizes a Chrome DevTools compatible interface to render captured traffic, allowing for the inspection of requests and responses from non-browser sources. It performs man-in-the-middle HTTPS decryption by generating a trusted root certificate to inspect encrypted communication between clients and servers. The project c

Mitmproxy is an interactive, programmable network proxy engine designed for traffic analysis and protocol manipulation. It functions as a gateway that intercepts, inspects, and modifies network traffic in real-time, supporting HTTP, HTTPS, WebSocket, DNS, and generic TCP or UDP streams. By acting as a trusted certificate authority, the proxy can dynamically generate and sign certificates to decrypt and analyze secure TLS-encrypted connections. The project distinguishes itself through a highly extensible, event-driven architecture that allows users to automate traffic transformation using cust

Dev-sidecar is a local HTTP proxy tool designed to optimize development environments by intercepting and modifying network traffic. It functions as a man-in-the-middle service that routes outgoing requests through custom endpoints, enabling developers to accelerate access to remote services, manage package registry connections, and bypass regional connectivity restrictions. The tool distinguishes itself through its ability to perform dynamic DNS resolution overrides and certificate-based traffic inspection, allowing for granular control over network paths and secure data analysis. It employs

Hetty is an HTTP intercepting proxy and web security research toolkit used to capture, inspect, and modify traffic between a browser and a server. It functions as an HTTP request editor for creating and replaying manual requests to test server behavior and as a project-based traffic logger that isolates network logs across different security research engagements. The tool provides a request-response interception loop that pauses outgoing requests and incoming responses in transit, allowing for manual editing or cancellation. It includes a manual request replay engine to construct and transmit

HTTP Toolkit is an open-source tool for debugging, testing and building with HTTP(S) on Windows, Linux & Mac.

Proxyman is a cross-platform HTTP debugging proxy that captures, inspects, and modifies HTTP, HTTPS, and WebSocket traffic. It functions as a man-in-the-middle proxy, decrypting SSL/TLS traffic to allow real-time inspection and modification of encrypted requests and responses. The tool is designed for debugging web and mobile applications, with capabilities for API mocking and simulation, scriptable traffic modification, and team collaboration on network logs. What distinguishes Proxyman is its deep integration with mobile and cross-platform development workflows. It provides automated certif

Web Debugging Proxy Application

PCAPdroid is an Android network traffic analyzer and packet capture tool that operates without requiring root access. It functions as a VPN-based firewall and network controller, capable of recording traffic in PCAPng format and blocking connections to specific domains or malicious hosts. The project distinguishes itself through a proxy-based system for decrypting TLS traffic and routing device network traffic through SOCKS5 proxies or the Tor network. It further allows for the modification of live HTTP requests and responses via custom scripts. Its capabilities cover application connection

AndroidHttpCapture is a mobile application for intercepting and analyzing HTTP and HTTPS network traffic directly on an Android device. It functions as a local proxy server and traffic interceptor to capture and monitor requests and responses from other installed mobile applications. The tool provides capabilities for MITM HTTPS decryption through root certificate installation and supports exporting captured network sessions as HAR files for external analysis. It allows for real-time response body injection and the modification of request headers via user agent spoofing. The project includes

An HTTP proxy library for Go

Fancyss is a network utility designed to function as a Shadowsocks proxy gateway. It operates as a transparent proxy manager that intercepts and routes network traffic at the gateway level, allowing for centralized management of internet access across all connected devices without requiring individual client-side configurations. The system employs policy-based routing and rule-based traffic filtering to direct data through specific network paths. It maintains multiple server connections simultaneously, utilizing failover-aware connection pooling to automatically switch traffic to healthy node