Configuring tmux

tmux reads ~/.tmux.conf when its server starts. A dozen lines turn the defaults from "fine" into "yours."

A sane starting config

# ~/.tmux.conf

# mouse: click panes, drag to resize, scroll the wheel
set -g mouse on

# keep more scrollback (default is 2000 lines)
set -g history-limit 10000

# windows renumber themselves when one closes (no gaps: 0,1,3)
set -g renumber-windows on

# numbering starts at 1, not 0 (easier to reach)
set -g base-index 1
setw -g pane-base-index 1

# longer to read the status messages (default: 750ms)
set -g display-time 2000

# snappier Escape key (default 500ms delay annoys vim users)
set -s escape-time 10

Every line above was loaded with tmux -f and confirmed with tmux show-options -g on tmux 3.4.

Reloading

Config is read when the server starts, not when you open a new terminal. After editing, reload without restarting:

From inside tmux: Ctrl-b : then type

source-file ~/.tmux.conf

Or from your shell:

tmux source-file ~/.tmux.conf

Check:

tmux show-options -g mouse

mouse on

Note: already-running sessions pick up most options, but base-index only affects new windows — old ones keep their numbers until recreated.

What each setting actually does

mouse on — the big one. Click to focus panes, drag borders to resize, scroll with the wheel (enters copy mode automatically). If you only change one thing, change this.
history-limit — lines of scrollback per pane. Logs scroll fast; 10000 is cheap (a few MB per pane at most).
renumber-windows — kill window 1 of 0,1,2 and the rest become 0,1 instead of leaving a gap.
escape-time — tmux waits this long after Escape to see if it's part of an escape sequence. 500ms makes vim feel laggy; 10ms is snappy. (Set to 0 and some terminals misbehave — 10 is the safe floor.)

What not to bother with yet

Status-bar theming, plugins (TPM), and copy-mode key rebinding are all real tmux hobbies — and all skippable until the basics are muscle memory. A plain status bar that shows session and window names is enough to work.