GridPlayer is a cross-platform desktop video player built on PyQt5 and libVLC that plays multiple videos simultaneously in a grid of cells. It supports local files and folders, M3U/PLS/XSPF playlists, YouTube/IPTV channel lists, and direct URLs resolved through yt-dlp and streamlink. The application routes resolved streams through an internal HTTP proxy when direct fetching is not viable, handles HLS/DASH live stream renewal, applies per-playlist settings overrides, and integrates SponsorBlock segment skipping. Its architecture is a monolith organized into a central Player widget with many focused managers (actions, grid, playlists, bookmarks, settings, window state), plus a multiprocessing layer that isolates VLC decoder instances and transfers decoded frames through safe shared memory. The GUI is extensive: custom dialogs, settings pages, overlays, drag-and-drop grid placement, tray integration, media session controls, and platform-specific integrations for Windows, macOS, and Linux/Wayland. This is purely an application; there is no data-research or analytics component beyond caching and metadata lookups that support playback.