The purists out there may be throwing their hands up in horror — a WYSIWYG interface! Letting users alter themes themselves! Well, yes, there is a risk on that. But the Customizer means that if you’re developing custom themes for client websites, you have a whole new set of tools to play with. The theme customizer allows users to tweak theme settings using a WYSIWYG interface and customise a theme so it includes pretty much anything they want.