Tmux

I already heard about tmux but never tried it. Now with fast growing pace of AI CLI tools like Claude Code and OpenCode, tmux seems like it could be helpful for managing multiple terminals. This article will be more of a way to have a quick reference on how i use tmux. There are already plenty of articles about tmux.

Quick Overview

Tmux is a terminal multiplexer to facilitate your life managing multiple terminal windows. How do you manage tabs within your browser? You have one or more instances of a browser (windows), and you create tabs inside each instance, right? you can also group tabs by topic if you want.

With tmux, is the same but for terminals, with a different nomenclature. You have sessions (like browser window instances) that keep running even if you close iTerm2 (terminal emulator I use on my mac), there is a concept of attachment where only one session can be attached at a time.

This is not an extensive overview of tmux, there are already plenty of tutorials with good info about that. This intents to be more of a quick reference on what and how to use tmux.

Core ideas

• Session = workspace
• Window = tab inside a session
• Pane = split inside a window
• Attached = a terminal is currently connected to that session
• Detached = the session is still running, but no terminal is connected to it
• Prefix = Ctrl+b
• Command Mode = Ctrl+b :

Sessions

Session shortcuts

Windows

Reorder windows (command mode)

Panes

Resize panes

macOS keyboard

Ctrl+b then Ctrl+↑↓←→

Command mode

Command mode

Open with Ctrl+b :, then type a command:

new-session -s mine
move-window -t 3
swap-window -t 3
resize-pane -R 10
setw synchronize-panes on
setw synchronize-panes off

Synchronize typing to all panes

Ctrl+b :
setw synchronize-panes on   # enable
setw synchronize-panes off  # disable

Optional toggle in ~/.tmux.conf:

bind e set-window-option synchronize-panes

Use with Ctrl+b e.

Fast window switching (no prefix)

To have this you first need to have all these panel numbers. To remove the panel 0, go to that panel then: Ctrl+b x

Add to ~/.tmux.conf:

bind -n M-1 select-window -t 1
bind -n M-2 select-window -t 2
bind -n M-3 select-window -t 3

• M-1 = Option+1 on Mac
• -n = no prefix needed
• Command key is NOT supported in tmux on macOS

Config file

nano ~/.tmux.conf                  # edit config
tmux source-file ~/.tmux.conf      # reload config

Closing iTerm2

Closing iTerm2 detaches the session — it does NOT kill it. Reattach anytime with tmux a -t session_name.

Quick reference — TLDR

tmux ls
tmux new -As work
tmux a -t work
tmux new -s mine -d
tmux rename-session -t oldname newname
tmux kill-ses -t mine
tmux source-file ~/.tmux.conf

Ctrl+b d          detach
Ctrl+b s          session picker
Ctrl+b $          rename session
Ctrl+b c          new window
Ctrl+b n / p      next/prev window
Ctrl+b 0-9        jump to window
Ctrl+b w          list windows
Ctrl+b ,          rename window
Ctrl+b &          close window
Ctrl+b .          move window
Ctrl+b "          split horizontal
Ctrl+b %          split vertical
Ctrl+b ←→↑↓       navigate panes
Ctrl+b z          zoom pane
Ctrl+b x          close pane
Ctrl+b :          command mode