GoodbyeDPI is a Windows-based Deep Packet Inspection (DPI) circumvention utility that bypasses ISP-imposed website blocks. It operates as a monolithic console application or Windows service that uses the WinDivert driver to intercept, analyze, and modify network packets at the NDIS layer. The software implements multiple evasion techniques including TCP fragmentation, HTTP header manipulation (Host header modification, spacing removal, case mixing), DNS redirection, and fake packet generation with altered TTL, checksum, or sequence numbers. It features a modular architecture with separate modules for packet filtering, connection tracking (DNS and TCP TTL), blacklist/whitelist management, and fake packet generation. The application runs with administrator privileges and supports both passive DPI (packet dropping) and active DPI circumvention (packet modification) strategies.