What is tmux?

tmux is a terminal multiplexer — it creates and manages multiple terminal sessions from a single window. Think of it as a window manager for your terminal.

NOTE:

The name comes from "terminal multiplexer" or "tmux" for short. It's pronounced "tee-mucks" but many developers just say "tmux".

Why use tmux?

Before tmux, you needed multiple terminal windows or SSH connections to work on different things. tmux gives you:

Persistent sessions: Programs keep running after you disconnect
Organization: Group related work into sessions, windows, and panes
Efficiency: Navigate between contexts without touching the mouse
Remote work: Start something on a server, detach, and reattach later

Installation

If tmux is installed, you'll see the version number. If not, install it:

macOS: brew install tmux
Ubuntu/Debian: sudo apt install tmux
Fedora: sudo dnf install tmux
Arch: sudo pacman -S tmux

Your first session

Start tmux with a named session:

You're now inside a tmux session. The bottom status line shows:

[mysession] 0:bash*

[mysession] is the session name
0:bash is window index and name
* marks the active window

You're in a normal shell — run commands like ls, vim, or any program. Everything runs inside tmux.

Detach and reattach

The magic happens when you detach — leave tmux without closing programs:

You're back at your normal terminal prompt. Any programs running in the session continue.

List your sessions:

Reattach to pick up where you left off:

NOTE:

This is why tmux is indispensable for remote servers. Start a long-running process (builds, tests, servers), detach, go home, and reattach later.

Prefix key

tmux uses a prefix key to distinguish tmux commands from shell commands. The default is Ctrl-b.

Press Ctrl-b, release both keys, then press the command key.

For example: Ctrl-b d detaches from the session.

NOTE:

Many users remap the prefix key. Ctrl-b is awkward (especially on keyboards where Ctrl requires reaching). Common alternatives: Ctrl-a (GNU screen's default) or Ctrl-space. We'll cover this in Step 7.

Common commands

Action	Command	Description
Start session	`tmux new -s name`	Create new named session
Detach	`tmux detach` or `Ctrl-b d`	Leave session running
List sessions	`tmux ls`	Show all sessions
Attach	`tmux attach -t name`	Reattach to session
Kill session	`tmux kill-session -t name`	Close session

Key bindings (prefix = Ctrl-b)

Key	Action
`d`	Detach from session
`?`	List all key bindings
`:`	Command prompt (enter commands by name)

Try it

Create a session: tmux new -s test
Run a long command: sleep 300
Detach: Ctrl-b d
List: tmux ls (you'll see test is still there)
Reattach: tmux attach -t test (your sleep is still running!)

NOTE:

Press Ctrl-b ? to see all key bindings. Press q or Esc to exit the help list.

Clean up

When done, exit the session:

Or kill it from outside:

Next: Step 2 → Sessions — Managing multiple sessions