The ‘auto-dim-other-buffers-mode’ is a global minor mode which makes windows without focus less prominent. With many windows in a frame, the idea is that this mode helps recognise which is the selected window by providing a non-intrusive but still noticeable visual indicator. The preferred way to install the mode is by grabbing ‘auto-dim-other-buffers’ package form MELPA: M-x package-install RET auto-dim-other-buffers RET Once installed, the mode can be turned on (globally) with: M-x auto-dim-other-buffers-mode RET To make the mode enabled every time Emacs starts, add the following to Emacs initialisation file (~/.emacs or ~/.emacs.d/init.el): (add-hook 'after-init-hook (lambda () (when (fboundp 'auto-dim-other-buffers-mode) (auto-dim-other-buffers-mode t)))) To configure how dimmed buffers look like, change `auto-dim-other-buffers-face' and `auto-dim-other-buffers-hide-face' faces. Those faces as well as other settings can be found in ‘auto-dim-other-buffers’ group which can be accessed with: M-x customize-group RET auto-dim-other-buffers RET Note that despite it’s name, since Emacs 27 the mode operates on *windows* rather than buffers. I.e. selected window is highlighted and all other windows are dimmed even if they display the same buffer. In older Emacs versions the mode falls back to the old behaviour where all windows displaying selected buffer are highlighted. This historic behaviour is where the mode gets its name from.