Using tmux synchronize-panes to Broadcast Commands Across Panes

Desired outcome

Enable tmux’s synchronize-panes option so that any keystrokes typed in the active pane are reproduced in every other pane of the same window. This lets you run a command once and see identical output across all panes.

Prerequisites

• tmux version 1.8 or later (the synchronize-panes option was introduced in 1.8).
• An active tmux session containing at least two panes, created with split-window (horizontal or vertical).

Procedure

1. Determine your tmux prefix; the default is Ctrl+b. If you have changed it, use that key combination.
2. Enter command mode: press the prefix, then :.
3. At the prompt, type set-option synchronize-panes on and press Enter.
4. (Optional) To make toggling easier, add a binding to your ~/.tmux.conf:

   bind C-s set-option synchronize-panes

   After saving, reload the configuration with tmux source-file ~/.tmux.conf (run inside a tmux pane).

Expected checks

• Verify the option is active: tmux show-options -g synchronize-panes should return on.
• In the active pane, type a simple command such as echo test and press Enter. Observe that the exact same line appears in every other pane.
• To confirm it is limited to input, run a command that produces different output in each pane (e.g., hostname on different machines) while synchronization is off; the outputs will differ, proving that only keystrokes are mirrored.

Recovery options

• Disable synchronization: prefix, :, then set-option synchronize-panes off followed by Enter.
• If you are about to run a potentially destructive command (e.g., rm, dd), turn synchronization off first to avoid executing it simultaneously in all panes.
• Closing or unlinking a pane removes it from the synchronized set; the remaining panes stay synchronized if the option remains on.

Limitations

The synchronize-panes option only mirrors incoming keystrokes. It does not copy existing pane contents, scrollback history, or output that is generated independently in each pane. Therefore, panes may diverge after running commands that produce different results, even while synchronization remains enabled.