In the ~/.tmux.conf file, you are able to define and override the values of
various options. Outside of explicitly setting an option, you may want to know
what its value is.
Perhaps it is unset, perhaps you don't remember, or maybe this particular session or pane is different than the global config.
Either from the CLI, you can run the tmux command to check:
$ tmux show-option -g history-limit
Or as a command to tmux, using your prefix:
:show-option -g history-limit
The -g flag will tell you the option's value as set globally for tmux. -w
for window, -p for pane, or no flag for the current session.
See man tmux for more details.