Where's the default tmux configuration file?

The default configuration is not available as a normal configuration file; it is part of the source code (thus built into the compiled program).

You can examine parts of the configuration with the commands list-keys and show-options:

tmux list-keys         # show current bindings

tmux show-options -s   # show current server options

tmux show-options -g   # show current global session options
tmux show-options      # show current session options

tmux show-options -gw  # show current global window options
tmux show-options -w   # show current window options

With tmux 1.7, show-options can also show you the value of a single option (prior versions can only list all the options from the specified class):

tmux show-options -gw window-status-format

If you are interested in the default configuration that a “pristine” server would have, then you can examine those items like this:

tmux -L unconfigured -f /dev/null start-server \; list-keys \; show-options -s \; show-options -g \; show-options -gw

The -L unconfigured bit specifies a server socket that you are probably not already using (if you happen to have a server using that socket name, then just pick some other, unused name). The -f /dev/null makes sure that the server does not use your normal ~/.tmux.conf configuration file (though, short of a custom build, there is no way to skip the /etc/tmux.conf system configuration file). The start-server command is necessary because only certain commands will automatically start a server.

If you are interested in looking at the source code here are the areas of interest:

• the options are defined in options-table.c in these arrays:
  • server_options_table
  • session_options_table
  • window_options_table
• the bindings start in key_bindings_init() in key-bindings.c, but some of the details are spread out with the individual command definitions (e.g. cmd_select_window_key_binding() in cmd-select-window.c).

There should be one in your $HOME/.tmux.conf specific to your user and a system-wide config file located at /etc/tmux.conf