When text is rendered by a computer, sometimes characters are displayed as substitute characters (typically small rectangles 􏿮). They represent the characters that cannot be displayed because no font with the necessary characters is installed on the computer, and have sometimes been called by the slang name tofu because of their visual similarity to the food of the same name.

Google's aim for Noto (whose name is derived from no tofu) is to remove this kind of 'tofu' from the Web.