feh is a lightweight, configurable X11 image viewer and cataloguer written in C. It provides multiple viewing modes: slideshow, index (montage), thumbnail browser, multiwindow, file list, and wallpaper setting. The application relies on Imlib2 for image loading and rendering, with optional support for libcurl (HTTP/HTTPS), libexif (EXIF metadata), Xinerama (multi-monitor), inotify (auto-reload), and libmagic (MIME detection). The codebase is modular, featuring reusable generic data structures (doubly linked list, hash table, Imlib2 wrapper) and a format specifier system for actions, captions, and titles. It is a mature, stable project with a long history (since 1999) and an extensive test suite using X11::GUITest. However, it shows signs of technical drift: manual memory management, legacy code comments, deprecated options, platform-specific conditionals, and reliance on external tools like dcraw and ImageMagick for certain image formats. The project is actively maintained with regular releases.