herbstluftwm is a tiling window manager based on Xlib and Glib that has a layout based on splitting frames and uses tags for multiple desktop functionality.
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Pro Offers a combination of manual and automatic tiling
Users can set up auto-tiling per app, or they can change any application to manual tiling to where they want on the screen.
Pro Can be reconfigured from the command line while it's still running
Configuration of herbstluftwm can be done live in the command line, so no booting in and out of the desktop is necessary.
Pro Highly customizable
Different layouts can be used in different frames on the same workspace, so the user can customize their layout to their liking on the fly.
Pro Uses a simple bash script for configuration
The configuration file for herbstluftwm is a bash script and is easily configurable.
Pro Great multi-monitor support
Herbstluftwm has built-in multi-monitor support that can customize to any size desired on the screen. This implies that the user is not held back by being forced to use each monitor's size.
Con No single window floating
The user cannot use floating for dialogs or anything else without making the entire workspace float. Their only choice is pseudo tiling.
Con No system tray
There is no system tray support in herbstluftwm. In that case, users who wish to have one must use an external application.