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. misuse 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 exception is if these characters are followed by a space or empty cell in which case kitty makes use of the extra cell to render them in two cells.

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 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. You can ssh in using the following command which will automatically copy the terminfo files to the server:

kitty +kitten ssh myserver

This ssh kitten takes all the same command line arguments as ssh, you can alias it to ssh in your shell’s rc files to avoid having to type it each time:

alias ssh="kitty +kitten ssh"

If for some reason that does not work (typically because the server is using a non POSIX compliant shell as /bin/sh), you can try using it with python instead:

kitty +kitten ssh use-python myserver

If that also fails, perhaps because python is not installed on the remote server, use the following one-liner instead (it is slower as it needs to ssh into the server twice, but will work with most servers):

infocmp -a xterm-kitty | ssh myserver tic -x -o \~/.terminfo /dev/stdin

If you are behind a proxy (like Balabit) that prevents this, you must redirect the 1st command to a file, copy that to the server and run tic manually. If you connect to a server, embedded or Android system that doesn’t have tic, copy over your local file terminfo to the other system as ~/.terminfo/x/xterm-kitty.

Really, the correct solution for this is to convince the OpenSSH maintainers to have ssh do this automatically, if possible, when connecting to a server, so that all terminals work transparently.

If the server is running FreeBSD, or another system that relies on termcap rather than terminfo, you will need to convert the terminfo file on your local machine by running (on local machine with kitty):

infocmp -C xterm-kitty

The output of this command is the termcap description, which should be appended to /usr/share/misc/termcap on the remote server. Then run the following command to apply your change (on the server):

cap_mkdb /usr/share/misc/termcap

Keys such as arrow keys, backspace, delete, home/end, etc. do not work when using su or sudo?

Make sure the TERM environment variable, is xterm-kitty. And either the TERMINFO environment variable points to a directory containing x/xterm-kitty or that file is under ~/.terminfo/x/.

Note that sudo might remove TERMINFO. Then setting it at the shell prompt can be too late, because command line editing may not be reinitialized. In that case you can either ask sudo to set it or if that is not supported, insert an env command before starting the shell, or, if not possible, after sudo start another Shell providing the right terminfo path:

sudo … TERMINFO=$HOME/.terminfo bash -i
sudo … env TERMINFO=$HOME/.terminfo bash -i
TERMINFO=/home/ORIGINALUSER/.terminfo exec bash -i

You can configure sudo to preserve TERMINFO by running sudo visudo and adding the following line:

Defaults env_keep += "TERM TERMINFO"

If you have double width characters in your prompt, you may also need to explicitly set a UTF-8 locale, like:

export LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8

How do I change the colors in a running kitty instance?

You can either use the OSC terminal escape codes to set colors or you can define keyboard shortcuts to set colors, for example:

map f1 set_colors --configured /path/to/some/config/file/colors.conf

Or you can enable remote control for kitty and use kitty @ set-colors. The shortcut mapping technique has the same syntax as the remote control command, for details, see kitty @ set-colors.

A list of pre-made color themes for kitty is available at: kitty-themes

Examples of using OSC escape codes to set colors:

Change the default foreground color:
printf '\x1b]10;#ff0000\x1b\\'
Change the default background color:
printf '\x1b]11;blue\x1b\\'
Change the cursor color:
printf '\x1b]12;blue\x1b\\'
Change the selection background color:
printf '\x1b]17;blue\x1b\\'
Change the selection foreground color:
printf '\x1b]19;blue\x1b\\'
Change the nth color (0 - 255):
printf '\x1b]4;n;green\x1b\\'

You can use various syntaxes/names for color specifications in the above examples. See XParseColor for full details.

If a ? is given rather than a color specification, kitty will respond with the current value for the specified color.

How do I specify command line options for kitty on macOS?

Apple does not want you to use command line options with GUI applications. To workaround that limitation, kitty will read command line options from the file <kitty config dir>/macos-launch-services-cmdline when it is launched from the GUI, i.e. by clicking the kitty application icon or using open -a kitty. Note that this file is only read when running via the GUI.

You can, of course, also run kitty from a terminal with command line options, using: /Applications/kitty.app/Contents/MacOS/kitty.

And within kitty itself, you can always run kitty using just kitty as it cleverly adds itself to the PATH.

I catted a binary file and now kitty is hung?

Never output unknown binary data directly into a terminal.

Terminals have a single channel for both data and control. Certain bytes are control codes. Some of these control codes are of arbitrary length, so if the binary data you output into the terminal happens to contain the starting sequence for one of these control codes, the terminal will hang waiting for the closing sequence. Press ctrl+shift+delete to reset the terminal.

If you do want to cat unknown data, use cat -v.

kitty is not able to use my favorite font?

kitty achieves its stellar performance by caching alpha masks of each rendered character on the GPU, so that every character needs to be rendered only once. This means it is a strictly character cell based display. As such it can use only monospace fonts, since every cell in the grid has to be the same size. Furthermore, it needs fonts to be freely resizable, so it does not support bitmapped fonts.

If your font is not listed in kitty list-fonts it means that it is not monospace or is a bitmapped font. On Linux you can list all monospace fonts with:

fc-list : family spacing outline scalable | grep -e spacing=100 -e spacing=90 | grep -e outline=True | grep -e scalable=True

Note that the spacing property is calculated by fontconfig based on actual glyph widths in the font. If for some reason fontconfig concludes your favorite monospace font does not have spacing=100 you can override it by using the following ~/.config/fontconfig/fonts.conf:

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<match target="scan">
    <test name="family">
        <string>Your Font Family Name</string>
    </test>
    <edit name="spacing">
        <int>100</int>
    </edit>
</match>
</fontconfig>

After creating (or modifying) this file, you may need to run the following command to rebuild your fontconfig cache:

fc-cache -r

Then, the font will be available in kitty list-fonts.

How can I assign a single global shortcut to bring up the kitty terminal?

Bringing up applications on a single key press is the job of the window manager/desktop environment. For ways to do it with kitty (or indeed any terminal) in different environments, see here.

How do I map key presses in kitty to different keys in the terminal program?

This is accomplished by using map with send_text in kitty.conf. For example:

map alt+s send_text normal,application \x13

This maps alt+s to ctrl+s. To figure out what bytes to use for the send_text you can use the show_key kitten. Run:

kitty +kitten show_key

Then press the key you want to emulate.

How do I open a new window or tab with the same working directory as the current window?

In kitty.conf add the following:

map f1 launch --cwd=current
map f2  launch --cwd=current --type=tab

Pressing F1 will open a new kitty window with the same working directory as the current window. The launch command is very powerful, explore its documentation.

Things behave differently when running kitty from system launcher vs. from another terminal?

This will be because of environment variables. When you run kitty from the system launcher, it gets a default set of system environment variables. When you run kitty from another terminal, you are actually running it from a shell, and the shell’s rc files will have setup a whole different set of environment variables which kitty will now inherit.

You need to make sure that the environment variables you define in your shell’s rc files are either also defined system wide or via the env directive in kitty.conf. Common environment variables that cause issues are those related to localization, such as LANG, LC_* and loading of configuration files such as XDG_*, KITTY_CONFIG_DIRECTORY.

To see the environment variables that kitty sees, you can add the following mapping to kitty.conf:

map f1 show_kitty_env_vars

then pressing F1 will show you the environment variables kitty sees.

This problem is most common on macOS, as Apple makes it exceedingly difficult to setup environment variables system-wide, so people end up putting them in all sorts of places where they may or may not work.

I am using tmux and have a problem

First, terminal multiplexers are a bad idea, do not use them, if at all possible. kitty contains features that do all of what tmux does, but better, with the exception of remote persistence (#391). If you still want to use tmux, read on.

Image display will not work, see tmux issue.

If you are using tmux with multiple terminals or you start it under one terminal and then switch to another and these terminals have different TERM variables, tmux will break. You will need to restart it as tmux does not support multiple terminfo definitions.

If you use any of the advanced features that kitty has innovated, such as styled underlines, desktop notifications, extended keyboard support, etc. they may or may not work, depending on the whims of tmux’s maintainer, your version of tmux, etc.

I opened and closed a lot of windows/tabs and top shows kitty’s memory usage is very high?

top is not a good way to measure process memory usage. That is because on modern systems, when allocating memory to a process, the C library functions will typically allocate memory in large blocks, and give the process chunks of these blocks. When the process frees a chunk, the C library will not necessarily release the underlying block back to the OS. So even though the application has released the memory, top will still claim the process is using it.

To check for memory leaks, instead use a tool like valgrind. Run:

PYTHONMALLOC=malloc valgrind --tool=massif kitty

Now open lots of tabs/windows, generate lots of output using tools like find/yes etc. Then close all but one window. Do some random work for a few seconds in that window, maybe run yes or find again. Then quit kitty and run:

massif-visualizer massif.out.*

You will see the allocations graph goes up when you opened the windows, then goes back down when you closed them, indicating there were no memory leaks.

For those interested, you can get a similar profile out of valgrind as you get with top by adding --pages-as-heap=yes then you will see that memory allocated in malloc is not freed in free. This can be further refined if you use glibc` as your C library by setting the environment variable MALLOC_MMAP_THRESHOLD_=64. This will cause free to actually free memory allocated in sizes of more than 64 bytes. With this set, memory usage will climb high, then fall when closing windows, but not fall all the way back. The remaining used memory can be investigated using valgrind again, and it will come from arenas in the GPU drivers and the per thread arenas glibc’s malloc maintains. These too allocate memory in large blocks and dont release it back to the OS immediately.