This minor mode highlights indentation levels via font-lock. Indent widths are dynamically discovered, which means this correctly highlights in any mode, regardless of indent width, even in languages with non-uniform indentation such as Haskell. This mode works properly around hard tabs and mixed indentation, and it behaves well in large buffers. To install, put this file in your load-path, and do M-x highlight-indent-guides-mode to enable it. To enable it automatically in most programming modes, use the following: (add-hook 'prog-mode-hook 'highlight-indent-guides-mode) To set the display method, use: (setq highlight-indent-guides-method METHOD) Where METHOD is either 'fill, 'column, 'character, or 'bitmap. To change the character used for drawing guide lines with the 'character method, use: (setq highlight-indent-guides-character ?ch) By default, this mode automatically inspects your theme and chooses appropriate colors for highlighting. To tweak the subtlety of these colors, use the following (all values are percentages): (setq highlight-indent-guides-auto-odd-face-perc 15) (setq highlight-indent-guides-auto-even-face-perc 15) (setq highlight-indent-guides-auto-character-face-perc 20) Or, to manually set the colors used for highlighting, use: (setq highlight-indent-guides-auto-enabled nil) (set-face-background 'highlight-indent-guides-odd-face "color") (set-face-background 'highlight-indent-guides-even-face "color") (set-face-foreground 'highlight-indent-guides-character-face "color")