For some reason, occasionally, an uppercase M appears at the right side of the window name, so the window name looks like this:


I'm pretty sure is because I'm pressing some combination that causes this. What is it and what does it means?

  • 5
    Finally someone who also felt my pain. – Karel Bílek Jul 31 '17 at 2:48
  • 1
    It also changed the stripe between panes from a nice thin line to a bright wide obnoxious thing. Cutting this off without wiping out my context is very nice. – chicks Nov 16 '18 at 16:21

From tmux(1):

    Mark the current pane (see select-pane -m).

So that means you've pressed C-b m (or equivalent in your environment) to mark that pane.

Marking a pane is useful for certain pane operations; from the section on select-pane:

The marked pane is the default target for -s to join-pane, swap-pane and swap-window.

To clear the mark, press C-b M. If you have M mapped to something else already, you can also use C-b : (to enter the tmux command prompt), followed by select-pane -M to clear the mark.

  • 24
    In my setup with mouse options turned on, right clicking a pane marks it. – paradroid Jul 4 '17 at 13:48
  • I've overwritten Prefix + M in my tmux. What command can I use to unmark the pane (without enabling mouse mode)? – byxor Oct 26 '17 at 14:11
  • 1
    PS, not everyone uses C-b as their prefix. – byxor Oct 26 '17 at 14:11
  • 3
    You can use C-b : followed by select-pane -M to clear the mark. The original answer does mention "or equivalent", but presumably most tmux users are aware that C-b is the default prefix. – jjlin Dec 6 '17 at 8:59

The list of window flags with their explanation can be found in man tmux /STATUS LINE, you’re looking for:

Symbol    Meaning
M         The window contains the marked pane.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.