# Glossary

os_window

  kitty has two kinds of windows. Operating System windows, refered to as OS Window, and kitty windows. An OS Window consists of one or more kitty tabs. Each tab in turn consists of one or more kitty windows organized in a layout.

tab

  A tab refers to a group of kitty windows, organized in a layout. Every OS Window contains one or more tabs.

layout

  A layout is a system of organizing kitty windows in groups inside a tab. The layout automatically maintains the size and position of the windows, think of a layout as a tiling window manager for the terminal. See Arrange windows for details.

window

  kitty has two kinds of windows. Operating System windows, refered to as OS Window, and kitty windows. An OS Window consists of one or more kitty tabs. Each tab in turn consists of one or more kitty windows organized in a layout.

overlay

  An overlay window is a kitty window that is placed on top of an existing kitty window, entirely covering it. Overlays are used throught kitty, for example, to display the the scrollback buffer, to display hints, for unicode input etc.

hyperlinks

  Terminals can have hyperlinks, just like the internet. In kitty you can control exactly what happens when clicking on a hyperlink, based on the type of link and its URL.

## Environment variables

Variables that influence kitty behavior

KITTY_CONFIG_DIRECTORY

  Controls where kitty looks for `kitty.conf` and other configuration files. Defaults to `~/.config/kitty`. For full details of the config directory lookup mechanism see, `kitty --config`.

VISUAL

  The terminal editor (such as `vi` or `nano`) kitty uses, when, for instance, opening `kitty.conf` in response to `ctrl+shift+f2`.

EDITOR

  Same as `VISUAL`. Used if `VISUAL` is not set.

Variables that kitty sets when running child programs

LANG

  This is set only on macOS, and only if the country and language from the macOS user settings form a valid locale.

KITTY_WINDOW_ID

  An integer that is the id for the kitty window the program is running in. Can be used with the kitty remote control facility.

KITTY_PID

  An integer that is the process id for the kitty process in which the program is running. Allows programs to tell kitty to reload its config by sending it the SIGUSR1 signal.

WINDOWID

  The id for the OS Window the program is running in. Only available on platforms that have ids for their windows, such as X11 and macOS.

TERM

  The name of the terminal, defaults to `xterm-kitty`. See `term`.

TERMINFO

  Path to a directory containing the kitty terminfo database.

COLORTERM

  Set to the value `truecolor` to indicate that kitty supports 16 million colors.

KITTY_LISTEN_ON

  Set when the remote control facility is enabled and the a socket is used for control via `kitty --listen-on` or `listen_on`. Contains the path to the socket. Avoids needs to use `kitty @ --to` when issuing remote control commands.

KITTY_PIPE_DATA

  Set to data describing the layout of the screen when running child programs using `launch --stdin-source` with the contents of the screen/scrollback piped to them.

KITTY_CHILD_CMDLINE

  Set to the command line of the child process running in the kitty window when calling the notification callback program on terminal bell, see `command_on_bell`.

KITTY_COMMON_OPTS

  Set with the values of some common kitty options when running kittens, so kittens can use them without needing to load kitty.conf.