Clicking beats describing
A static screen invites opinions about colour. A prototype someone can click invites questions about whether the flow makes sense. Moving that conversation earlier saves a round of revisions that would otherwise arrive after the visual design is finished.
One file, no version confusion
Working in a shared file removes the exchange of dated exports that used to consume a day of every project. Clients comment in place, and the comment stays attached to the thing it refers to.
Components keep the system honest
Building a component library early means an inconsistency shows up while it is still cheap to fix. It also means the handover to build starts from a structure that already matches how the front end will be assembled.
Where we still leave it
Prototypes are poor at conveying motion timing and terrible at conveying real content density. We move to the browser earlier than most, because a page full of real text answers questions a prototype cannot.
