Unlike copyediting, which focuses purely on the text, proofreaders engage with the book after the interior has been designed and laid out. That means that in addition to keeping an eye out for egregious grammar errors and typos, the proofreader is focused on aesthetics: eliminating typographic gaffes such as widows, orphans, and runts; marking bad breaks and word stacks; and ensuring design elements such as subheads and running heads are handled consistently.