- macOS 10.15.5
- tmux 3.1b
macOS has ncurses version 5.7 which does not ship the terminfo description for tmux. There're two ways that can help you to solve this problem.
Instead of tmux-256color, use screen-256color which comes with system. Place this command into ~/.tmux.conf or ~/.config/tmux/tmux.conf(for version 3.1 and later):
set-option default-terminal "screen-256color"
The screen-256color in most cases is enough and more portable solution. But it does not support any italic font style.
Unfortunately, The latest (6.2) ncurses version does not work properly. Make sure to use ncurses which comes with macOS:
$ which tic
/usr/bin/tic
If you see another path to terminal info compiler, you must fix the $PATH for a shell, or uninstall a local ncurses by using a package manager.
Let's download and unpack the latest nucurses terminal descriptions:
$ curl -LO https://invisible-island.net/datafiles/current/terminfo.src.gz && gunzip terminfo.src.gz
And compile tmux-256color terminal info. The result is placed into ~/.terminfo:
$ /usr/bin/tic -xe tmux-256color terminfo.src
If you want to use tmux-256color for all users, use sudo. The result is placed into /usr/share/terminfo:
$ sudo /usr/bin/tic -xe tmux-256color terminfo.src
You may also to compile few more infos, it is up to you:
$ /usr/bin/tic -xe alacritty-direct,tmux-256color terminfo.src
If you see something like:
"terminfo.src", line 1650, terminal 'pccon+base': enter_bold_mode but no exit_attribute_mode
"terminfo.src", line 1650, terminal 'pccon+base': enter_reverse_mode but no exit_attribute_mode
do not worry, all should be fine. Make sure that you can use the compiled description:
$ infocmp -x tmux-256color
And finally, set default terminal in tmux configuration file:
set-option default-terminal "tmux-256color"
Also, do not forget to enable RGB colors (24 bit colors, or true colors, as you like). The $TERM outside tmux must support 256 colors. Also, it must contains Tc or RGB flag in terminfo description:
$ tmux info | grep -e RGB -e Tc
If both are missing, then you need to override terminal description in tmux configuration file:
set-option -a terminal-overrides ",XXX:RGB"
where XXX is a terminal outside tmux, like xterm-256color. And finally, terminal-overrides suports a pattern matching:
set-option -a terminal-overrides ",*256col*:RGB"
If you use Alacritty terminal, make sure the $TERM outside tmux is alacritty-direct. The alacritty terminal description does not have RGB flag. Otherwise, override description:
set-option -a terminal-overrides ",alacritty:RGB"