Why it matters
Prototypes catch the expensive mistakes while they're still cheap: confusing flows, missing steps, wrong assumptions about what users understand. Watching five people use a prototype teaches more than fifty opinions about static designs.
How it works
Design tools (Figma, mainly) link screens with hotspots: tap here, go there. Realistic content and key paths matter more than coverage: you prototype the journeys that carry risk, then put them in front of users and watch where they hesitate.
What to do about it
Before any significant build, insist on walking the prototype yourself as a customer would, and if possible, watch two or three real users try it. Every stumble found here is a change order avoided later.
