i3 is a dynamic window manager that is targeted at advanced users and developers. It uses clean and documented code in order to allow for ease of configuration.
Ranked in these QuestionsQuestion Ranking
Pro Fully configurable (including tiling)
One of the biggest attractions of i3 is that it can be configured just about any way the user likes. Ranging from custom keyboard shortcuts to placement of opened apps, it is up to the user as to how they would like their window manager to behave.
Pro Easily readable plain-text configuration
i3 has plain-text configuration, meaning that no lua or haskell is needed. This makes it rather easy to recommend i3 to other people without worrying whether or not they have the knowledge to configure it as it can be read by anyone without prior knowledge.
Pro Easily switch to and manage floating windows
i3 can allow for the user to manage floating windows. Floating mode can be toggled by pressing $mod+Shift+Space. This way the user can take advantage of tiling as well as floating windows, all in the same session.
Pro Windows can be turned into Tabs
i3 permits tabbing through windows by turning on Tab mode with $mod+w.
This shortcut can be changed in config file.
Pro Fast, especially on weaker hardware
Tiling means there are no fancy compositing or window effects to take up system resources.
Pro Can stack
i3 allows for stacking of windows in its environment.
Pro RandR support
RandR provides more information about your outputs and connected screens than Xinerama does. To be specific, the code which handled on-the-fly screen reconfiguration (meaning without restarting the X server) was a very messy heuristic approach and most of the time did not work correctly — that is just not possible with the limited information that Xinerama offers (just a list of screen resolutions and no identifiers for the screens or any additional information). Xinerama simply was not designed for dynamic configuration.
Pro Can be reloaded quickly and configured without a client restart
Just two hot keys: Shift+Super+C to reload the config and Shift+Super+R to restart (which takes less than one second). Restarts pick up new versions of i3 or the updated config file, so you can upgrade to a newer version or quickly see the changes to i3 without quitting your X session.
Pro No window borders
Screen area is not wasted by window decorations. This allows programs to use the entire screen.
NOTE: Default config has window title bar enabled so there is a little screen space lose on the top of the screen.
Pro VIM Style key bindings
You can configure i3 so that your keys for moving windows is similar to vim, for example, M-j to move the window down.
Pro Never have to take hands off keyboard
Keyboard shortcut based navigation can seem daunting at first, but one quickly gets used to it. It enables the user to never have to take their hands off the keyboard, meaning that they can use their computer quickly and efficiently.
Pro Simple to use
Configuration is nearly automatic and simple, which can be really helpful to beginners.
Pro Configuration allow multi-monitor support
User can assign specific workspaces to specific displays as well as apps to workspaces. This makes possible opening set of most used apps with 1 shortcut always on the same screens.
Pro Terminal bell can be used to notify of completed actions
Terminal-bell gets passed through and marks the workspace visibly.
Pro Sane development process
i3 uses test driven development with an extensive test suite to prevent bugs from ever happening again. All external contributions require a thorough code review to guarantee a certain level of quality.
Pro Layouts can be saved and reused
Pro Great choice for keyboard users
The user keeps their hands in one spot (most of the time). One will find that the mouse is used less and less, making navigation quicker over time.
Con Missing "include" possibility in config
While pretty good and easy to use for common tasks, the configuration language is missing the
include directive common in other languages. You can use a workaround - a shell script to config parts on demand. It would be best if this were built-in however.
Con Poor floating window support
Sometimes this is necessary, even when the Dev rejects feature requests. Firefox child windows (option dialog) is an example.
Con No shortcut to switch between two recently used applications/windows
You can easily switch between two workspaces but not two windows (which are not adjacent to each other). The functionality simply isn't there and the dev refuses to include it as a part of i3 core. This can get annoying when you have multiple windows in the same workspace. There is a manual workaround though.
Con Steep learning curve
Has a steep learning curve for beginners.
Con Not very configurable
Unlike XMonad or Awesome, i3 can't be configured in a turing complete language, so it is much harder to alter its core functionality to do exactly what the user wants.
Con Cannot share workspaces between monitors
You have to pick and choose which workspaces go where, which effectively halves the number of workspaces you have. The developer refuses to allow this feature.
Con It has some issues with transparency
Using transparent windows can cause them to crash.
Con Manual tiling
The layout isn't automatic. The user must move panels manually and may indeed end up spending time on that rather than on working with the application.
Con A program running on Discrete GPU may have problem rendering
That is a common issue with laptops which renders some programs in discrete GPU but passes the frames through integrated GPU to display. This makes it pain to play games on laptops using discrete GPU.
Con The plain-text configuration may not be suitable for beginners
i3 is configured through a plaintext configuration file. While it's very powerful and easy to learn, it may not be entirely user-friendly for those who have never edited a text configuration.
Con Documentation is online
Can't access it offline unless you download the page.