The different types of social proof include expert social proof, celebrity social proof, user social proof, and wisdom of the crowd social proof. Expert social proof is when an expert or authority figure endorses a product or service. Celebrity social proof is when a celebrity endorses a product or service. User social proof is when customers or users of a product or service provide positive reviews or testimonials. Wisdom of the crowd social proof is when a large group of people are seen to be using a product or service.