The Customizer has been around since WordPress 3.4, yet it is one of the most unknown and under appreciated features around. We will start out by learning what the Customizer is, from where users can access it, and why it is so awesome. Then we’ll proceed to theme mods, the Customizer API, how to integrate it in your themes and plugins, and dive into how you can extend existing functionality. Finally We’ll cover some tutorials and example implementations, what default themes do with it, and how [who?] encourages its use.