Online apparel is an extremely lucrative category. Experts predict that the worldwide e-commerce segment of fashion and apparel will grow from $408 billion in 2017 to more than $706 billion by 2023. As you might expect, with opportunity comes competition. According to one study, 26 percent of the top 1000 e-commerce sites are dedicated apparel retailers. The same study suggests that while Amazon continues to dominate e-commerce, 75.1 percent of online clothing sales come from retailers that specialize in clothing, accessories or shoes.