What if your terminal couldn’t scroll back? When I just started using Tmux I didn’t know how to scroll back so I used to run Rails Server in a seperate terminal.

When I finally figured out how to scroll back up I also learned the hard way that you have to scroll down or otherwise your Rails server (and the whole app) will hang.

There are 2 ways of scrolling in Tmux. You can configure them in your .tmux.conf and they can be used together.

1 - With your mouse

Almost every setting in Tmux can be applied while running Tmux and through the .tmux.conf config file. Applying settings while running Tmux is a convenient way to test if they do what you expect. If  you press ctrl + b then type

:set -g mouse on

Scrolling with your mouse should work now. To make this setting permanent you have to add it to your config without th colon in front of it. Tmux has 2 config files: ~/.tmux.conf in your home directory for your personal settings and /etc/tmux.conf for the system wide config file. I recommend that you only make changes to your personal config. That will also override any setting made in the system wide config.

2 - With keyboard shortcuts

Scrolling with keys is enabled by default in Tmux. Just press ctrl + b then [ to move around with the arrow keys.

If you have recent Macbook with the tiny unusable arrow keys you can use vim-keys or emacs keys as well. To test it while running Tmux use:

:setw mode-keys emacs


:setw mode-keys vi

Just as with the mouse settings you have to add them to your .tmux.conf to make them permanent. Some people use set-window-option in stead of setw, it’s the same. setw is an alias for set-window-option.

If you want to scroll all the way back down you just press enter. This also stops your app from hanging when rails server is outputting a lot of data.

Here is a short list of key combinations you can use:

Function                     vi              emacs

--------                     --              -----

Half page down               C-d             M-Down
Half page up                 C-u             M-Up
Next page                    C-f             Page down
Previous page                C-b             Page up
Scroll down                  C-Down or C-e   C-Down
Scroll up                    C-Up or C-y     C-Up
Search again                 n               n
Search again in reverse      N               N
Search backward              ?               C-r
Search forward               /               C-s

Note that you have to press ctrl-b twice if you use that for page up since ctrl-b is bound as the command key.