Vroom is perhaps the closest competitor to Carvana: It also offers an all-online, car-buying experience, but as the newer kid on the block, its inventory isn’t as large. CarMax, on the other hand, dwarfs both online retailers — it’s the largest used car seller in the country. But until recently, buying still required a trip to a physical dealership. Like its online rivals, it promises a “stress-free,” no-price-negotiation experience. These aren’t your only choices — there are plenty of online car-buying sites and apps.