= kitty - A terminal emulator
:toc:
:toc-placement!:
// START_SHORTCUT_BLOCK
:sc_close_tab: pass:quotes[`ctrl+shift+q`]
:sc_close_window: pass:quotes[`ctrl+shift+w`]
:sc_copy_to_clipboard: pass:quotes[`ctrl+shift+c`]
:sc_decrease_font_size: pass:quotes[`ctrl+shift+minus`]
:sc_eighth_window: pass:quotes[`ctrl+shift+8`]
:sc_fifth_window: pass:quotes[`ctrl+shift+5`]
:sc_first_window: pass:quotes[`ctrl+shift+1`]
:sc_fourth_window: pass:quotes[`ctrl+shift+4`]
:sc_increase_font_size: pass:quotes[`ctrl+shift+equal`]
:sc_input_unicode_character: pass:quotes[`ctrl+shift+u`]
:sc_move_tab_backward: pass:quotes[`ctrl+shift+,`]
:sc_move_tab_forward: pass:quotes[`ctrl+shift+.`]
:sc_move_window_backward: pass:quotes[`ctrl+shift+b`]
:sc_move_window_forward: pass:quotes[`ctrl+shift+f`]
:sc_move_window_to_top: pass:quotes[`ctrl+shift+``]
:sc_new_os_window: pass:quotes[`ctrl+shift+n`]
:sc_new_tab: pass:quotes[`ctrl+shift+t`]
:sc_new_window: pass:quotes[`ctrl+shift+enter`]
:sc_next_layout: pass:quotes[`ctrl+shift+l`]
:sc_next_tab: pass:quotes[`ctrl+shift+right`]
:sc_next_window: pass:quotes[`ctrl+shift+]`]
:sc_ninth_window: pass:quotes[`ctrl+shift+9`]
:sc_pass_selection_to_program: pass:quotes[`ctrl+shift+o`]
:sc_paste_from_clipboard: pass:quotes[`ctrl+shift+v`]
:sc_paste_from_selection: pass:quotes[`ctrl+shift+s` or `shift+insert`]
:sc_previous_tab: pass:quotes[`ctrl+shift+left`]
:sc_previous_window: pass:quotes[`ctrl+shift+[`]
:sc_restore_font_size: pass:quotes[`ctrl+shift+backspace`]
:sc_scroll_end: pass:quotes[`ctrl+shift+end`]
:sc_scroll_home: pass:quotes[`ctrl+shift+home`]
:sc_scroll_line_down: pass:quotes[`ctrl+shift+down` or `ctrl+shift+j`]
:sc_scroll_line_up: pass:quotes[`ctrl+shift+up` or `ctrl+shift+k`]
:sc_scroll_page_down: pass:quotes[`ctrl+shift+page_down`]
:sc_scroll_page_up: pass:quotes[`ctrl+shift+page_up`]
:sc_second_window: pass:quotes[`ctrl+shift+2`]
:sc_seventh_window: pass:quotes[`ctrl+shift+7`]
:sc_show_scrollback: pass:quotes[`ctrl+shift+h`]
:sc_sixth_window: pass:quotes[`ctrl+shift+6`]
:sc_tenth_window: pass:quotes[`ctrl+shift+0`]
:sc_third_window: pass:quotes[`ctrl+shift+3`]
:sc_toggle_fullscreen: pass:quotes[`ctrl+shift+f11`]
// END_SHORTCUT_BLOCK

++++
<img align="left" role="left" src="logo/kitty.png?raw=true"/>
++++
image::https://travis-ci.org/kovidgoyal/kitty.svg?branch=master[Build status, link=https://travis-ci.org/kovidgoyal/kitty]

== Major Features

* Uses OpenGL for rendering, offloads rendering to the GPU for lower system
load and buttery smooth scrolling. Uses threaded rendering to minimize input
latency.

* Supports all modern terminal features: graphics (images), unicode,
true-color, OpenType ligatures, mouse protocol, focus tracking, bracketed paste and so on.

* Supports tiling multiple terminal windows side by side in different
layouts without needing to use an extra program like tmux

* Can be controlled from scripts or the shell prompt, even over SSH.

* Supports startup sessions which allow you to specify the window/tab layout,
working directories and programs to run on startup.

* Cross-platform support: kitty currently works on Linux and macOS, but because
it uses only OpenGL for rendering, it should be trivial to port to other
platforms.

* Allows you to open the scrollback buffer and window contents in a separate
window using arbitrary programs of your choice. This is useful for browsing
the history comfortably in a pager or editor and also for doing things like
opening URLs using only the keyboard.


image::screenshot.png?raw=true[Screenshot, showing three programs in the "Tall" layout]

toc::[]


== Installation

kitty is designed to run from source, for easy hackability. Make sure
the following dependencies are installed first.

=== Dependencies

* python >= 3.5
* harfbuzz >= 1.5.0
* zlib
* libpng
* freetype (not needed on macOS)
* fontconfig (not needed on macOS)
* ImageMagick (optional, needed to use the `kitty icat` tool to display images in the terminal)
* gcc or clang (required only for building)
* pkg-config (required only for building)
* For building on Linux in addition to the above dependencies you might also need to install the `-dev` packages for `xcursor`, `xrandr`, `xinerama` and `xkbcommon-x11`, if they are not already installed by your distro.

=== Install and run from source

....
git clone https://github.com/kovidgoyal/kitty && cd kitty
....

Now build the C parts of kitty with the following command:

....
make
....

You can run kitty, as:

....
python3 .
....

=== Linux packages

* Arch Linux: AUR git package https://aur.archlinux.org/packages/kitty-git/

* Arch Linux: AUR stable package https://aur.archlinux.org/packages/kitty/

* NixOS / nixpkgs: https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/kitty/default.nix


=== macOS packages

kitty is available as a macOS `dmg` file for easy installation from the
link:../../releases[releases page].  You can also run kitty directly from
source using the above install from source instructions, after installing its
dependencies using http://brew.sh/[brew] or a similar package manager.


== Design philosophy

kitty is designed for power keyboard users. To that end all its controls
work with the keyboard (although it fully supports mouse interactions as
well). Its configuration is a simple, human editable, single file for
easy reproducibility (I like to store config files in source control).

The code in kitty is designed to be simple, modular and hackable. It is
written in a mix of C (for performance sensitive parts) and Python (for
easy hackability of the UI). It does not depend on any large and complex
UI toolkit, using only OpenGL for rendering everything.

Finally, kitty is designed from the ground up to support all modern
terminal features, such as unicode, true color, bold/italic fonts, text
formatting, etc. It even extends existing text formatting escape codes,
to add support for features not available elsewhere, such as colored and
styled (curly) underlines. One of the design goals of kitty is to be
easily extensible so that new features can be added in the future with
relatively less effort.

== Tabs and Windows

kitty is capable of running multiple programs organized into tabs and
windows. The top level of organization is the _Tab_. Each tab consists
of one or more _windows_. The windows can be arranged in multiple
different layouts, like windows are organized in a tiling window
manager. The keyboard controls (which are all customizable) for tabs and
windows are:

[[scrolling-shortcuts]]
[options="header"]

=== Scrolling

|===
|Action |Shortcut

|Scroll line up   | {sc_scroll_line_up}
|Scroll line down | {sc_scroll_line_down}
|Scroll page up   | {sc_scroll_page_up}
|Scroll page down | {sc_scroll_page_down}
|Scroll to top    | {sc_scroll_home}
|Scroll to bottom | {sc_scroll_end}

|===

[options="header"]

=== Tabs

|===
|Action |Shortcut

|New tab   | {sc_new_tab}
|Close tab | {sc_close_tab}
|Next tab  | {sc_next_tab}
|Previous tab | {sc_previous_tab}
|Next layout | {sc_next_layout}
|Move tab forward | {sc_move_tab_forward}
|Move tab backward | {sc_move_tab_backward}

|===


[options="header"]

=== Windows

|===
|Action |Shortcut

|New window   | {sc_new_window}
|New OS window| {sc_new_os_window}
|Close window | {sc_close_window}
|Next window  | {sc_next_window}
|Previous window | {sc_previous_window}
|Move window forward | {sc_move_window_forward}
|Move window backward | {sc_move_window_backward}
|Move window to top | {sc_move_window_to_top}
|Focus specific window (windows are counted clockwise from the top left corner) | {sc_first_window}, {sc_second_window} ... {sc_tenth_window}

|===

=== Miscellaneous

|===
|Action |Shortcut

|Increase font size   | {sc_increase_font_size}
|Decrease font size   | {sc_decrease_font_size}
|Restore font size    | {sc_restore_font_size}
|Toggle fullscreen    | {sc_toggle_fullscreen}
|Input unicode character | {sc_input_unicode_character}
|Pass current selection to program | {sc_pass_selection_to_program}
|===


== Controlling kitty from scripts

You can control kitty from the command line/scripts by sending it messages.
You can tell kitty to open/close/rename tabs and windows. You can even send
arbitrary input/text to any specified window. Messages can be sent using
`kitty @`. Note that you must set `allow_remote_control yes` in your
kitty.conf to use this feature.  It even works over SSH connections.  This
feature is best illustrated with a link:remote-control.asciidoc[tutorial].


== The scrollback buffer

kitty supports scrolling back to view history, just like most terminals. You
can use either the <<scrolling-shortcuts,keyboard shortcuts>> or the mouse
scroll wheel to do so.  However, kitty has an extra, neat feature. Sometimes
you need to explore the scrollback buffer in more detail, maybe search for some
text or refer to it side-by-side while typing in a follow-up command. kitty
allows you to do this by pressing the {sc_show_scrollback} key-combination,
which will open the scrollback buffer in your favorite pager program (which is
`less` by default). Colors and text formatting are preserved. You can explore
the scrollback pager comfortably within the pager.


== Miscellaneous features

You can double click to select a word and triple click to select a line. You can also
hold down `ctrl+shift` and click on a URL to open it in a browser.


== Layouts

Currently, there are five layouts available,

* Stack -- Only a single maximized window is shown at a time
* Tall -- One window is shown full height on the left, the rest of the windows are shown one below the other on the right
* Grid -- All windows are shown in a grid
* Horizontal -- All windows are shown side-by-side
* Vertical -- All windows are shown one below the other

You can switch between layouts using the {sc_next_layout} key combination.

Writing a new layout only requires about fifty lines of code, so if there is
some layout you want, take a look at link:kitty/layout.py[layout.py] and submit
a pull request!


== Configuration

kitty is highly customizable, everything from keyboard shortcuts, to
painting frames-per-second. See the heavily commented
link:kitty/kitty.conf[default config file]. By default kitty looks for a
config file in the OS config directory (usually
`~/.config/kitty/kitty.conf` on Linux and
`~/Library/Preferences/kitty/kitty.conf` on macOS) but you can pass a specific
path via the `--config` option.

== Startup Sessions

You can control the tabs, window layout, working directory, startup
programs, etc. by creating a "session" file and using the `--session`
command line flag. For example:

....
# Set the window layout for the current tab
layout tall
# Set the working directory for windows in the current tab
cd ~
# Create a window and run the specified command in it
launch zsh
launch vim
# Set the title for the next window
title Chat with x
launch irssi --profile x

# Create a new tab (the part after new_tab is the optional tab name which will
# be displayed in the tab bar, if omitted, the title of the active window will
# be used instead)
new_tab my tab
cd ~/somewhere
# Set the layouts allowed in this tab
enabled_layouts tall, stack
# Set the current layout
layout stack
launch zsh
# Make the current window the active (focused) window
focus
launch emacs
....

== Protocol Extensions

kitty has a few extensions to the xterm protocol, to enable advanced features,
see link:protocol-extensions.asciidoc[Protocol Extensions].


== Font control

kitty has extremely flexible and powerful font selection features. You can
specify individual families for the regular, bold, italic and bold+italic
fonts. You can even specify specific font families for specific ranges of
unicode characters. This allows precise control over text rendering. It can
come in handy for applications like powerline, without the need to use patched
fonts. See the various font related configuration directives in the
link:kitty/kitty.conf[config file].

== Performance

The main goals for kitty performance are user perceived latency while typing
and "smoothness" while scrolling as well as CPU usage. kitty tries hard to find
an optimum balance for these. To that end it keeps a cache of each rendered
glyph in video RAM so that font rendering is not a bottleneck.  Interaction
with child programs takes place in a separate thread from rendering, to improve
smoothness.

There are two parameters you can tune to adjust the performance. ``repaint_delay``
and ``input_delay``. These control the artificial delays introduced into the
render loop to reduce CPU usage. See the link:kitty/kitty.conf[config file] for details.

You can generate detailed per-function performance data using
link:https://github.com/gperftools/gperftools[gperftools]. Build kitty with
`make profile` which will create an executable called `kitty-profile`.  Run
that and perform the task you want to analyse, for example, scrolling a large
file with `less`. After you quit, function call statistics will be printed to
`stdout` and you can use tools like *kcachegrind* for more detailed analysis.

Here are some CPU usage numbers for the task of scrolling a file continuously in less.
The CPU usage is for the terminal process and X together and is measured using htop.
The measurements are taken at the same font and window size for all terminals on a
`Intel(R) Core(TM) i7-4820K CPU @ 3.70GHz` CPU with a
`Advanced Micro Devices, Inc. [AMD/ATI] Cape Verde XT [Radeon HD 7770/8760 / R7 250X]` GPU.

|===
| Terminal | CPU usage (X + terminal)

| kitty    | 6 - 8%
| xterm    | 5 - 7% (but scrolling was extremely janky)
| termite  | 10 - 13%
| urxvt    | 12 - 14%
| gnome-terminal | 15 - 17%
| konsole  | 29 - 31%

|===

As you can see, kitty uses much less CPU than all terminals, except xterm, but
its scrolling "smoothness" is much better than that of xterm (at least to my,
admittedly biased, eyes).

== Note for Linux/macOS packagers

While kitty does use python, it is not a traditional python package, so please do not install it in site-packages.
Instead run,

```
python3 setup.py linux-package
```

This will install kitty into the directory `linux-package`. You can run kitty
with `linux-package/bin/kitty`.  All the files needed to run kitty will be in
`linux-package/lib/kitty`. The terminfo file will be installed into
`linux-package/share/terminfo`. Simply copy these files into `/usr` to install
kitty. In other words, `linux-package` is the staging area into which kitty is
installed. You can choose a different staging area, by passing the `--prefix`
argument to `setup.py`.

You should probably split kitty into two packages, `kitty-terminfo` that
installs the terminfo file and `kitty` that installs the main program.
This allows users to install the terminfo file on servers into which they ssh,
without needing to install all of kitty.

This applies to creating packages for kitty for macOS package managers such as
brew or MacPorts as well.


== Frequently Asked Questions

=== Some special symbols are rendered small/truncated in kitty?

The number of cells a unicode character takes up are controlled by the unicode
standard.  All characters are rendered in a single cell unless the unicode
standard says they should be rendered in two cells. When a symbol does not fit,
it will either be rescaled to be smaller or truncated (depending on how much
extra space it needs). This is often different from other terminals which just
let the character overflow into neighboring cells, which is fine if the
neighboring cell is empty, but looks terrible if it is not.

Some programs, like powerline, vim with fancy gutter symbols/status-bar, etc.
use unicode characters from the private use area to represent symbols. Often
these symbols are square and should be rendered in two cells.  However, since
private use area symbols all have their width set to one in the unicode
standard, kitty renders them either smaller or truncated. The correct solution
for this is to use either use different symbols that are not square, or to use
a font that defines ligatures with the space character for these symbols. See
link:https://github.com/kovidgoyal/kitty/issues/182[#182] for a discussion of
the approach using ligatures.

=== How do I build kitty.app on macOS?

Install `optipng` and `librsvg` using `brew` or similar (needed for the logo generation step).

And run:
```
make app
```

This `kitty.app` unlike the released one does not include its own copy of
python and the other dependencies. So if you ever un-install/upgrade those dependencies
you might have to rebuild the app.

Note that the released kitty.dmg includes all dependencies, unlike the
`kitty.app` built above and is built automatically by using the `kitty` branch of
link:https://github.com/kovidgoyal/build-calibre[build-calibre] however, that
is designed to run on Linux and is not for the faint of heart.


=== Using a color theme with a background color does not work well in vim?

First make sure you have not changed the TERM environment variable, it should
be `xterm-kitty`. vim uses *background color erase* even if the terminfo file
does not contain the `bce` capability. This is a bug in vim. You can work around
it by adding the following to your vimrc:

....
let &t_ut=''
....

See link:https://github.com/kovidgoyal/kitty/blob/master/protocol-extensions.asciidoc#setting-text-styles-colors-in-arbitrary-regions-of-the-screen[here]
for why kitty does not support background color erase.

== I get errors about the terminal being unknown or opening the terminal failing when SSHing into a different computer?

This happens because the kitty terminfo files are not available on the server. Either install kitty on the server,
or simply copy over the terminfo files, using:

....
ssh myserver mkdir -p \~/.terminfo
infocmp xterm-kitty | ssh myserver "cat > /tmp/kitty.terminfo"
ssh myserver tic -x -o \~/.terminfo /tmp/kitty.terminfo
....

Really, the correct solution for this is to convince the OpenSSH maintainers to have ssh do this
automatically when connecting to a server.

== A tribute

While over the decades I am sure many people have contributed to the
development of the terminal emulator space, there is one individual in
particular I would like to thank. link:http://invisible-island.net[Thomas E.
Dickey], the creator of xterm.  xterm is the most comprehensive and
feature-rich terminal emulator I have had the pleasure of using. As I worked on
kitty, I ran headlong into more and more gnarly corners of terminal behavior.
On all those occasions, either the excellent documentation at
link:http://invisible-island.net/xterm/ctlseqs/ctlseqs.html[xterm-ctlseqs] or
investigating the behavior and code of xterm or vttest were invaluable tools to
aid my understanding.

My achievements, if any, in developing kitty would not have been possible without
his prior work and the generous sharing of knowledge accumulated over decades.

Thank you.


== Resources on terminal behavior

http://invisible-island.net/xterm/ctlseqs/ctlseqs.html

https://en.wikipedia.org/wiki/C0_and_C1_control_codes

http://vt100.net/