Frequently Asked Questions - kitty
Description: 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 un...

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# 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 wide 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 en-space (U+2002) in which case kitty makes use of the extra cell to render them in two cells. This behavior can be turned off for specific symbols using `narrow_symbols`.

As of version 0.40 kitty has innovated a new protocol that allows programs running in the terminal to control how many cells a character is rendered in thereby solving the issue of character width once and for all.

Similarly, some monospaced font families are buggy and have bold or italic faces that have characters wider than the width of the normal face, these will also result in clipping. Such issues should be reported to the font developer. Monospaced font families must have all their characters rendered within a fixed width across all faces of the font, otherwise they aren’t really monospaced.

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

First, be sure to use a color scheme in vim instead of relying on the terminal theme. Otherwise, background and text selection colours may be difficult to read.

Sadly, vim has very poor out-of-the-box detection for modern terminal features. Furthermore, it recently broke detection even more. It kind of, but not really, supports terminfo, except it overrides it with its own hard-coded values when it feels like it. Worst of all, it has no ability to detect modern features not present in terminfo, at all, even security sensitive ones like bracketed paste.

Thankfully, probably as a consequence of this lack of detection, vim allows users to configure these low level details. So, to make vim work well with any modern terminal, including kitty, add the following to your `~/.vimrc`.

    " Mouse support
    set mouse=a
    set ttymouse=sgr
    set balloonevalterm
    " Styled and colored underline support
    let &t_AU = "\e[58:5:%dm"
    let &t_8u = "\e[58:2:%lu:%lu:%lum"
    let &t_Us = "\e[4:2m"
    let &t_Cs = "\e[4:3m"
    let &t_ds = "\e[4:4m"
    let &t_Ds = "\e[4:5m"
    let &t_Ce = "\e[4:0m"
    " Strikethrough
    let &t_Ts = "\e[9m"
    let &t_Te = "\e[29m"
    " Truecolor support
    let &t_8f = "\e[38:2:%lu:%lu:%lum"
    let &t_8b = "\e[48:2:%lu:%lu:%lum"
    let &t_RF = "\e]10;?\e\\"
    let &t_RB = "\e]11;?\e\\"
    " Bracketed paste
    let &t_BE = "\e[?2004h"
    let &t_BD = "\e[?2004l"
    let &t_PS = "\e[200~"
    let &t_PE = "\e[201~"
    " Cursor control
    let &t_RC = "\e[?12$p"
    let &t_SH = "\e[%d q"
    let &t_RS = "\eP$q q\e\\"
    let &t_SI = "\e[5 q"
    let &t_SR = "\e[3 q"
    let &t_EI = "\e[1 q"
    let &t_VS = "\e[?12l"
    " Focus tracking
    let &t_fe = "\e[?1004h"
    let &t_fd = "\e[?1004l"
    execute "set <FocusGained>=\<Esc>[I"
    execute "set <FocusLost>=\<Esc>[O"
    " Window title
    let &t_ST = "\e[22;2t"
    let &t_RT = "\e[23;2t"

    " vim hardcodes background color erase even if the terminfo file does
    " not contain bce. This causes incorrect background rendering when
    " using a color theme with a background color in terminals such as
    " kitty that do not support background color erase.
    let &t_ut=''

These settings must be placed before setting the `colorscheme`. It is also important that the value of the vim `term` variable is not changed after these settings.

## I get errors about the terminal being unknown or opening the terminal failing or functional keys like arrow keys don’t work?

These issues all have the same root cause: the kitty terminfo files not being available. The most common way this happens is SSHing into a computer that does not have the kitty terminfo files. The simplest fix for that is running:

    kitten ssh myserver

It will automatically copy over the terminfo files and also magically enable shell integration on the remote machine.

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

    alias s="kitten ssh"

If this does not work, see Copying terminfo files manually for alternative ways to get the kitty terminfo files onto a remote computer.

The next most common reason for this is if you are running commands as root using sudo or su. These programs often filter the `TERMINFO` environment variable which is what points to the kitty terminfo files.

First, make sure the `TERM` is set to `xterm-kitty` in the sudo environment. By default, it should be automatically copied over.

If you are using a well maintained Linux distribution, it will have a `kitty-terminfo` package that you can simply install to make the kitty terminfo files available system-wide. Then the problem will no longer occur.

Alternately, you can configure sudo to preserve `TERMINFO` by running `sudo visudo` and adding the following line:

    Defaults env_keep += "TERM TERMINFO"

If none of these are suitable for you, you can run sudo as

    sudo TERMINFO="$TERMINFO"

This will make `TERMINFO` available in the sudo environment. Create an alias in your shell rc files to make this convenient:

    alias sudo="sudo TERMINFO=\"$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

## I cannot use the key combination X in program Y?

First, run:

    kitten show-key -m kitty

Press the key combination X. If the kitten reports the key press that means kitty is correctly sending the key press to terminal programs. You need to report the issue to the developer of the terminal program. Most likely they have not added support for Comprehensive keyboard handling in terminals.

If the kitten does not report it, it means that the key is bound to some action in kitty. You can unbind it in `kitty.conf` with:

    map X no_op

Here X is the keys you press on the keyboard. So for example `ctrl`+`shift`+`1`.

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

The easiest way to do it is to use the themes kitten, to choose a new color theme. Simply run:

    kitten themes

And choose your theme from the list.

You can also 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 kitten @ set-colors. The shortcut mapping technique has the same syntax as the remote control command, for details, see kitten @ set-colors.

To change colors when SSHing into a remote host, use the `color_scheme` setting for the ssh kitten.

Additionally, You can use the OSC terminal escape codes to set colors. 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. The contents of the file are assumed to be the command line to pass to kitty in shell syntax, for example:

    --single-instance --override background=red

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, and rendering them all in parallel. 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.

Note

If you are trying to use a font patched with Nerd Fonts symbols, don’t do that as patching destroys fonts. There is no need, kitty has a builtin NERD font and will use it for symbols not found in any other font on your system. If you have patched fonts on your system they might be used instead for NERD symbols, so to force kitty to use the pure NERD font for NERD symbols, add the following line to `kitty.conf`:

    # Nerd Fonts v3.3.0

    symbol_map U+e000-U+e00a,U+ea60-U+ebeb,U+e0a0-U+e0c8,U+e0ca,U+e0cc-U+e0d7,U+e200-U+e2a9,U+e300-U+e3e3,U+e5fa-U+e6b7,U+e700-U+e8ef,U+ed00-U+efc1,U+f000-U+f2ff,U+f000-U+f2e0,U+f300-U+f381,U+f400-U+f533,U+f0001-U+f1af0 Symbols Nerd Font Mono

Those Unicode symbols not in the Unicode private use areas are not included.

If your font is not listed in `kitten choose-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

On macOS, you can open Font Book and look in the Fixed width collection to see all monospaced fonts on your system.

Note that on Linux, 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 `kitten choose-fonts`.

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

Use the panel kitten, this allows you to use kitty as a quick access Quake like terminal and even to use kitty as the desktop background, if so desired.

## I do not like the kitty icon!

The kitty icon was created as tribute to my cat of nine years who passed away, as such it is not going to change. However, if you do not like it, there are many alternate icons available, click on an icon to visit its homepage:

You can put `kitty.app.icns` (macOS only) or `kitty.app.png` in the kitty configuration directory, and this icon will be applied automatically at startup. On X11 and Wayland, this will set the icon for kitty windows. Note that not all Wayland compositors support the protocol needed for changing window icons.

Unfortunately, on macOS, Apple’s Dock does not change its cached icon so the custom icon will revert when kitty is quit. Run the following to force the Dock to update its cached icons:

    rm /var/folders/*/*/*/com.apple.dock.iconcache; killall Dock

If you prefer not to keep a custom icon in the kitty config folder, on macOS, you can also set it with the following command:

    # Set kitty.icns as the icon for currently running kitty
    kitty +runpy 'from kitty.fast_data_types import cocoa_set_app_icon; import sys; cocoa_set_app_icon(*sys.argv[1:]); print("OK")' kitty.icns

    # Set the icon for app bundle specified by the path
    kitty +runpy 'from kitty.fast_data_types import cocoa_set_app_icon; import sys; cocoa_set_app_icon(*sys.argv[1:]); print("OK")' /path/to/icon.png /Applications/kitty.app

You can also change the icon manually by following the steps:

1. Find `kitty.app` in the Applications folder, select it and press `⌘`+`I`

2. Drag `kitty.icns` onto the application icon in the kitty info pane

3. Delete the icon cache and restart Dock:

    rm /var/folders/*/*/*/com.apple.dock.iconcache; killall Dock

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

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

    map alt+s send_key ctrl+s
    map ctrl+alt+2 combine : send_key ctrl+c : send_key h : send_key a

This causes the program running in kitty to receive the `ctrl`+`s` key when you press the `alt`+`s` key and several keystrokes when you press `ctrl`+`alt`+`2`. To see this in action, run:

    kitten show-key -m kitty

Which will print out what key events it receives. To send arbitrary text rather than a key press, see `send_text` instead.

## 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` and, most importantly, `PATH` to locate binaries.

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/zellij 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.

Using ancient versions of tmux such as 1.8 will cause gibberish on screen when pressing keys (#3541).

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.

Displaying images while inside programs such as nvim or ranger may not work depending on whether those programs have adopted support for the unicode placeholders workaround that kitty created for tmux refusing to support images.

If you use any of the advanced features that kitty has innovated, such as styled underlines, desktop notifications, variable sized text, extended keyboard support, file transfer, the ssh kitten, shell integration 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 don’t release it back to the OS immediately.

## Why does kitty sometimes start slowly on my Linux system?

kitty takes no longer (within 100ms) to start than other similar GPU terminal emulators, (and may be faster than some). If kitty occasionally takes a long time to start, it could be a power management issue with the graphics card. On a multi-GPU system (which many modern laptops are, having a power efficient GPU that’s built into the processor and a power hungry dedicated one that’s usually off), even if the answer of the GPU will only be “don’t use me”.

For example, if you have a system with an AMD CPU and an NVIDIA GPU, and you know that you want to use the lower powered card to save battery life and because kitty does not require a powerful GPU to function, you can choose not to wake up the dedicated card, which has been reported on at least one system (#4292) to take ≈2 seconds, by running kitty as:

    MESA_LOADER_DRIVER_OVERRIDE=radeonsi __EGL_VENDOR_LIBRARY_FILENAMES=/usr/share/glvnd/egl_vendor.d/50_mesa.json kitty

The correct command will depend on your situation and hardware. `__EGL_VENDOR_LIBRARY_FILENAMES` instructs the GL dispatch library to use `libEGL_mesa.so` and ignore `libEGL_nvidia.so` also available on the system, which will wake the NVIDIA card during device enumeration. `MESA_LOADER_DRIVER_OVERRIDE` also assures that Mesa won’t offer any NVIDIA card during enumeration, and will instead just use `radeonsi_dri.so`.