Free, open-source alternatives to Magnet

A window manager that snaps windows into halves, thirds and quarters by dragging them to screen edges or using keyboard shortcuts.

Magnet arranges windows into tiles. Drag a window to an edge or corner, pick a position from the menu bar or press a shortcut, and it fills a half, third, quarter or the whole screen, across several displays.

The apps below do the same job of snapping individual windows into screen regions on demand, rather than tiling every window automatically. Rectangle and Nudge follow Magnet's model most closely, with edge snapping and shortcuts for fixed positions. Loop picks a position from a radial menu around the pointer, MacsyZones lets you draw your own zone layouts and drop windows into them, and Penc snaps windows into halves and quarters with trackpad swipes.

Magnet website