Multisite is often treated as a dark corner of WordPress and can be forgotten or managed poorly when developing public plugins or working on client projects.
Let’s pull back the curtain and shed some light.
We’ll cover a brief history of multisite to give context to some of the early decisions. We’ll walk through the structure and load process to show how straightforward multisite really is. We’ll go through the brand new WP_Site_Query and WP_Network_Query class introduced in WordPress 4.6. And we’ll cover some common solutions to things people frequently want to do with multisite.