i3 (window manager)

• Possess well-written, documented code that encourages user contribution.[3]
• Use XCB instead of Xlib.
• Implement multi-monitor features correctly, so that each workspace is assigned to a virtual screen, and monitor additions and removals are non-destructive of windows.
• Implement different modes, similar to the text editor vi and vim. That is, keys have different functions depending on the mode that the window manager is in.
• Use a tree as the abstraction (and underlying data structure) for window management.
• Implement UTF-8 character encoding.

• The configuration is done via a plain text file (found in ~/.config/i3/config).
• i3 can be customized without programming.[6]
• Contrary to other popular tiling window managers, such as dwm, awesome, and xmonad, window management is left to the user in i3. Windows are held inside containers, which can be split vertically or horizontally. They can also optionally be resized. There are also options for stacking the windows, as well as tabbing them (similar to the interface that web browsers use).
• Uses dmenu as the default program launcher, but it can be replaced.[6][8]

Even though i3 is a tiling window manager, specific windows, such as password pop-ups, are not displayed as new tiles by default;[9] they are stacked in front of tiled windows. These floating windows can be moved and resized freely, just as they can in popular desktop environments like GNOME or KDE Plasma.[8]

The authors of i3 intend floating windows to be used for pop-up windows only.[10]

• 
  i3 with stacked layout
• 
  i3 with tabbed layout
• 
  i3 with floating window