A style guide, also referred to as a pattern library, is a living document that details the front-end code for all the elements and modules of a website or application. It also documents the site’s visual language, from header styles to color palettes. In short, a proper style guide is a one-stop guide that the entire team can reference when considering site changes and iterations. Susan Robertson shows us how to build and maintain a style guide that helps everyone from product owners and producers to designers and developers keep an ever-changing site on brand and on target.