what is rectangle fr?

Rectangle is a window management app for macOS that lets you move and resize windows quickly using keyboard shortcuts or by dragging them to screen edges. If you've ever wished you could snap a window to fill exactly the left half of your screen, the way Windows does when you drag a window to the edge, Rectangle brings that same kind of control to Mac. The core idea is simple: instead of manually dragging and resizing application windows, you press a key combination and Rectangle instantly repositions the active window to a preset layout. Common layouts include halves (left, right, top, bottom), quarters (each corner), thirds, and maximized. You can also drag a window to a screen edge or corner to trigger the same snaps visually, seeing a preview footprint before you release the mouse. Beyond basic snapping, Rectangle supports moving windows to different monitors, centering windows, almost-maximizing (leaving a small gap around the window), and adjusting window size incrementally. If a particular app already uses a keyboard shortcut that conflicts with Rectangle, you can tell Rectangle to ignore that app entirely. Rectangle is built in Swift and works on macOS 10.15 and later. It is the open-source successor to the older Spectacle app, with additional actions and improvements over its predecessor. Someone who works with many open windows simultaneously, developers, writers, or anyone doing side-by-side comparisons, would find it a practical tool for staying organized without reaching for the mouse.