True Color (24-bit) and italics with alacritty + tmux + vim (neovim)

alacritty-tmux-vim_truecolor.md

True Color (24-bit) and italics with alacritty + tmux + vim (neovim)

This should make True Color (24-bit) and italics work in your tmux session and vim/neovim when using Alacritty (and should be compatible with any other terminal emulator, including Kitty).

Testing colors

Running this script should look the same in tmux as without.

curl -s https://gist.githubusercontent.com/lifepillar/09a44b8cf0f9397465614e622979107f/raw/24-bit-color.sh >24-bit-color.sh
bash 24-bit-color.sh

Configuration files

⚠️ IMPORTANT ⚠️ Don't set $TERM in your shell (zshrc, bashrc, etc.), but your terminal (alacritty).

Alacritty

In ~/.config/alacritty/alacritty.yml:

env:
  TERM: xterm-256color

tmux

In ~/.tmux.conf (or ~/.config/tmux/tmux.conf):

set -g default-terminal "tmux-256color"
set -ag terminal-overrides ",xterm-256color:RGB"

# Or use a wildcard instead of forcing a default mode.
# Some users in the comments of this gist have reported that this work better.
#set -sg terminal-overrides ",*:RGB"

# You can also use the env variable set from the terminal.
# Useful if you share your configuration betweeen systems with a varying value.
#set -ag terminal-overrides ",$TERM:RGB"

vim

In ~/.vimrc:

" You might have to force true color when using regular vim inside tmux as the
" colorscheme can appear to be grayscale with "termguicolors" option enabled.
if !has('gui_running') && &term =~ '^\%(screen\|tmux\)'
  let &t_8f = "\<Esc>[38;2;%lu;%lu;%lum"
  let &t_8b = "\<Esc>[48;2;%lu;%lu;%lum"
endif

syntax on
set termguicolors
colorscheme yourfavcolorscheme

neovim

If you use ~/.vimrc for your nvim configuration, use the above vim example because it's fully compatible.

💡 neovim recently (Dec 6th 2023) merged some changes that detects termguicolors automatically, so there's no need to set this in an upcoming release. I'll update this notice with a version once released as a public version. This came with the 0.10 release (May 16th 2024).

In ~/.config/nvim/init.vim

set termguicolors
colorscheme yourfavcolorscheme

Or ~/.config/nvim/init.lua:

vim.o.termguicolors = true
vim.cmd'colorscheme yourfavcolorscheme'

Not working correctly ?

Check out the comments below for possible solutions.

And if you found another solution I would really appreciate if you left a comment with instructions and the following information:

• OS/Distro + version
• Vim or Neovim + version
• Terminal name + version

Mentions

Shout-out to the nice folks that provided insightful feedback:

• @mikeslattery native neovim termguicolors support
• @mikeslattery black and white vim colorscheme
• @sahibalejandro env variable inside tmux configuration
• @wonbinbk wildcard in tmux terminal configuration

I find that when I press backspace inside tmux, it convert to white space. also the color is also inconsisent outside and inside tmux

MacOS : 12.6
Vim : 9.0
Alacritty : 0.11.0

inside alacritty.yml:

font:
  normal:
    family: Menlo 

  size: 14.0

Inside .vimrc:

set background=dark
if !has('gui_running') && &term =~ '^\%(screen\|tmux\)'
  let &t_8f = "\<Esc>[38;2;%lu;%lu;%lum"
  let &t_8b = "\<Esc>[48;2;%lu;%lu;%lum"
endif
syntax on
set termguicolors
colorscheme onedark

Inside .tmux.conf:

set -g default-terminal "tmux-256color"
set -ag terminal-overrides ",xterm-256color:RGB"

@sokinpui The phenomenon I encountered before is the same as yours. You can try this set of configurations. It works for me.

alacrity

env:
  TERM: screen-256color

tmux

set -g default-terminal "screen-256color"
set-option -sa terminal-overrides ',screen-256color:Tc'

Hey 👋
This combination of settings works fine for me

# .alacritty.yml

env:
  TERM: alacritty

and in my tmux config:

# tmux.conf

set-option -g default-terminal "screen-256color"

• OS/Distro: MacOS Ventura 13.6
• Vim: VIM - Vi IMproved 9.0
• Terminal: alacritty 0.12.3 (5efb069)
• Tmux: tmux 3.3a

Hope it can help ✌️

Alacritty versions >= 0.13.0 (moved to TOML for config)

[env]
TERM="xterm-256color"

Italics in my vim were messed up, if someone has this problem, you can verify by running

echo -e "\e[3mitalic\e[0m"

if output is in italics then it's a vim problem, otherwise something else is wrong.

I had to add the following in my vimrc as per this for italics.

let &t_ZH="\e[3m"
let &t_ZR="\e[23m"

using macvim, tmux and iterm2

Thank you so much for this..

I legit switched to kitty for months over this issue, I had tried every fix out there (what did it was the ENV) so glad to be back with alacritty

AMAZING!!! Thanks

BREAKING NEWS!

(edits: I was wrong. Only the neovim changes aren't necessary.)

tl;dr - This gist is no longer necessary with latest Neovim.

Neovim now checks for 256 color compatibility and automatically sets termguicolors. Alacritty with default $TERM value ("alacritty") works fine. I just tested it with nightly.

Recent changes announced at the Neovim conference a few days ago have made the changes in this gist unnecessary for latest builds. However, I'm sure as of this moment many people are using versions that don't yet support this and that will likely be the case for a few weeks. I don't know the exact version this was added, or which versions have it other than latest nightly.

Of course, it will still be necessary for Vim.

Thanks for the heads-up @mikeslattery ! This is great news :)

I'll update this article and follow up when this goes into a public release.

Looks like I wasn't correct. You still need the tmux and alacritty config. You just don't need the neovim config anymore.

Quick test for Linux. As of this comment it works for nightly and not for release.

#!/bin/bash
# Test for truecolor.  Should see bands of smooth gradient colors.

# To test  installed nvim, set this to "nvim" and comment out #linux nvim install block, and remove rm $NVIM line
NVIM=/tmp/nvim

# Linux nvim install
NIGHTLY=https://github.com/neovim/neovim/releases/download/nightly/nvim.appimage
RELEASE=https://github.com/neovim/neovim/releases/download/stable/nvim.appimage
# Change to $NIGHTLY to see it working correctly.
curl -Lo $NVIM $RELEASE
chmod +x $NVIM

# Reconfigure
echo '
set -ag terminal-overrides ",xterm-256color:RGB"
' > /tmp/.tmux.conf
echo '
env:
  TERM: xterm-256color
' > /tmp/alacritty.yaml

# Test
TEST=https://gist.githubusercontent.com/lifepillar/09a44b8cf0f9397465614e622979107f/raw/24-bit-color.sh
alacritty --config-file /tmp/alacritty.yaml \
  -e tmux -f /tmp/.tmux.conf -L nvim new-session \
  $NVIM --clean  "+terminal curl -s $TEST | bash" "+set termguicolors?"
# old way:
# $NVIM --clean  +"set termguicolors" "+colorscheme ron" "+terminal curl -s $TEST | bash"

# Cleanup
rm "$NVIM"
rm /tmp/.tmux.conf /tmp/alacritty.yaml

Appreciate the detailed follow-up on this @mikeslattery. I've updated the article to reflect this 👍

echo 'set -as terminal-overrides ",'"$(echo ${TERM%%-*})"'*:Tc"' >> ~/.tmux.conf

---

https://github.com/tmux/tmux/wiki/FAQ#how-do-i-use-rgb-colour

tmux must be told that the terminal outside supports RGB colour. This is done by specifying the RGB or Tc terminfo(5) flags. RGB is the official flag, Tc is a tmux extension.

With tmux 3.2 and later this can be added with the terminal-features option:

set -as terminal-features ",gnome*:RGB"

Or for any tmux version the terminal-overrides option:

set -as terminal-overrides ",gnome*:Tc"

and replace gnome with the result of echo ${TERM%%-*} (the first part of $TERM delimited by -) from the terminal emulator that you are currently using outside tmux such as putty or xterm.

Just what I needed, thank you a lot.

My configuration:

alacritty 0.13.2
NVIM v0.9.5

.tmux.conf

# Fix Colors
set -g default-terminal "screen-256color"
set -ag terminal-overrides ",xterm-256color:RGB

alacritty.toml

[env]
TERM="xterm-256color"

config neovim

vim.opt.termguicolors = true

My configuration:

zsh 5.9
tmux 3.4
alacritty 0.13.2
NVIM v0.10.0-dev-3135+g7acf39dda

.tmux.conf

set -g default-terminal "tmux-256color"
set -sg terminal-overrides ",*:RGB"

.config/nvim/init.vim

if $COLORTERM ==# 'truecolor'
  set termguicolors
else
  set guicursor=
endif

nothing special on alacritty.toml and .zshrc
i didn't set env TERM explicitly. but i have

$ env | rg TERM
COLORTERM=truecolor
TERM=tmux-256color
TERM_PROGRAM=tmux
TERM_PROGRAM_VERSION=3.4

Thanks for this!

@LeFede This worked for me with Arch/Alacritty/tmux

alacritty.yaml

env:
  TERM: alacritty-direct

tmux.conf

set-option -a terminal-overrides ",alacritty:RGB"

default-terminal was not needed in the tmux.conf

This worked for me. Thanks so much for adding this information!

On a Wayland / Hyprland setup

My .tmux.conf only has the line:

set -g default-terminal "screen-256color"

I added to alacritty.toml, which seemed to be the key:

[colors]
transparent_background_colors = true
[window]
opacity = 0.8

Immediately both neovim and tmux started showing transparency. I did not have to explicitly set vim.opt.termguicolors = true in my neovim conf.

I've only added the following to alacritty.toml (i.e.: using a default tmux config) and it seems to work as expected.

[env]
TERM = "alacritty-direct"

Undercurls, italics, bold, strikethrough, etc. also work.

Worked out of the box on Arch! Thanks!

Heads up that it's not enough to source your tmux config after making changes to it (i.e. with tmux source /path/to/tmux.conf), I needed to kill the session and start a new one for the true colors to take effect

~/.tmux.conf

# Включение поддержки true color
set -g default-terminal "xterm-256color"
set -ga terminal-overrides ',xterm-256color:Tc'

# Включение поддержки мыши
set -g mouse on

~/.config/alacritty/alacritty.toml

[terminal.shell]
program = "tmux"
args = []

[env]
# Без этого в tmux true color не работает
TERM = "alacritty-direct"

~/.config/vim/vimrc

" Используем 20-битные цвета
set termguicolors

OSX Ventura Alacritty 0.12.2 tmux 3.3a nvim 0.9.2

Problem

When using neovim within tmux, my colors were off and it would not display italics or undercurls.

Solution

I had trouble with the provided solution, but it pointed me in the right direction. This is what works for me.

alacritty

I left the env: section commented out

tmux.conf

set-option -sa terminal-features ',alacritty:RGB'
set-option -ga terminal-features ",alacritty:usstyle"
set-option -ga terminal-overrides ',alacritty:Tc'
set -g default-terminal "alacritty"

nvim

termguicolors = true

MacOS Monterey use this setting and work! Thank man

echo 'set -as terminal-overrides ",'"$(echo ${TERM%%-*})"'*:Tc"' >> ~/.tmux.conf

https://github.com/tmux/tmux/wiki/FAQ#how-do-i-use-rgb-colour

tmux must be told that the terminal outside supports RGB colour. This is done by specifying the RGB or Tc terminfo(5) flags. RGB is the official flag, Tc is a tmux extension.
With tmux 3.2 and later this can be added with the terminal-features option:
set -as terminal-features ",gnome*:RGB"
Or for any tmux version the terminal-overrides option:
set -as terminal-overrides ",gnome*:Tc"

and replace gnome with the result of echo ${TERM%%-*} (the first part of $TERM delimited by -) from the terminal emulator that you are currently using outside tmux such as putty or xterm.

I've tried everything else in this thread, this was the only thing that solved it for me running Ubuntu 22.04.5 LTS with tmux 3.2a and neovim v0.10.0-dev. Bless your beautiful shell skills!

Thanks alot for this, it worked! 😄

Fedora 41, Alacritty 0.14.0, tmux 3.5a, nvim 0.10.2

What worked for me was @ericragsdale solution:

alacritty:
nothing in the env section

tmux.conf:

set-option -sa terminal-features ',alacritty:RGB'
set-option -ga terminal-features ",alacritty:usstyle"
set-option -ga terminal-overrides ',alacritty:Tc'
set -g default-terminal "alacritty"

thanks!

@bogdanp05 I use the exact same software versions as you (Fedora, Alacrity, tmux, nvim). The default solution ITT worked for me.

using Nix Home manager

programs.tmux = {
  enable = true;
  extraConfig = ''
    #Configure True Colors
    set -g default-terminal "tmux-256color"
    set -ag terminal-overrides ",xterm-256color:RGB"
  '';
};

programs.alacritty = {
  enable = true;
  env = {
    TERM = "xterm-256color";
  };
};

This dose not represent my current setting but will leave it here for completeness see my next comment

---

FYI any using wsl with alarcitty installed on windows these colour issues, I resolved them with;

alacritty.toml

[env]
TERM = "alacritty"
WSLENV="TERM/u:USERPROFILE/u"

If you get an error about not being able to find the term alacritty when opening Ubuntu follow Post Build. I did the following;

1. Installed all the dependency's required for Ubuntu and alacritty
2. Used cargo to build alacritty on my WSL instance
3. Installed the Terminfo as described in the post-build above; FYI; I had to clone the ropo then ran tic pointing at my repo

After that my setting my tmux.conf to finally did the trick

set-option -sa terminal-features ',alacritty:RGB'
set-option -ga terminal-features ",alacritty:usstyle"
set-option -ga terminal-overrides ',alacritty:Tc'
set -g default-terminal "alacritty"

Run this with bash, not sh. Learned this the hard way

@JoaoFelipe3, thanks for the comment I wanted to update this but completely lost the ticker. After reading the docs from tmux I settled on a different config that has been working for the last few moths.

set -g default-terminal 'tmux-256color'

set -as terminal-overrides ',*:Setulc=\E[58::2::::%p1%{65536}%/%d::%p1%{256}%/%{255}%&%d::%p1%{255}%&%d%;m'
set -as terminal-overrides ',*:Smulx=\E[4::%p1%dm'
set -as terminal-features ',*:usstyle'
set -as terminal-features ',xterm*:RGB'
set -as terminal-features ',alacritty*:RGB'

The main note is from the tmux docs It says to use default-terminal 'tmux-256color' and the above is working for me.

[env]
TERM = "alacritty"
LC_CTYPE = "en_US.UTF-8"
WSLENV="TERM/u:USERPROFILE/u"