tmux set-option -g prefix ½ This works for me: unbind C-b set-option -g prefix C-g bind-key C-g send-prefix but this does not: unbind C-b set-option -g prefix ½ bind-key ½ send-prefix How can I use the ½ key as prefix? $ tmux -V tmux 2.6 $ locale LANG=C LANGUAGE=C LC_CTYPE="en_US.UTF-8" LC_NUMERIC="en_US.UTF-8" LC_TIME="en_US.UTF-8" LC_COLLATE="en_US.UTF-8" LC_MONETARY="en_US.UTF-8" LC_MESSAGES="en_US.UTF-8" LC_PAPER="en_US.UTF-8" LC_NAME="en_US.UTF-8" LC_ADDRESS="en_US.UTF-8" LC_TELEPHONE="en_US.UTF-8" LC_MEASUREMENT="en_US.UTF-8" LC_IDENTIFICATION="en_US.UTF-8" LC_ALL=en_US.UTF-8

Support for Unicode keys was added in tmux 2.3. Are you sure your tmux is new enough?

Does `tmux show -g prefix` show the change? Did you remember to restart tmux entirely after changing .tmux.conf?