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

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

colors

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.

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:

@ericragsdale
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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

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

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'

@nickgnd
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nickgnd commented Oct 24, 2023

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 ✌️

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

[env]
TERM="xterm-256color"

@Hritik14
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Hritik14 commented Nov 7, 2023

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

@PThorpe92
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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

@jonnovaretti
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AMAZING!!! Thanks

@mikeslattery
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mikeslattery commented Dec 11, 2023

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.

@andersevenrud
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Author

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.

@mikeslattery
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mikeslattery commented Dec 13, 2023

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 $NIGHTLY
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

@andersevenrud
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Author

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

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