If it seems like Amazon dominates most online retail categories, that’s because it does.
According to a new Q1 2018 study by marketing analytics platform Jumpshot, Amazon has more than 80% market share across categories on average. It has higher shares for commodity products like batteries (97%), tools (93%) and cleaning supplies (88%), for which many consumers care less about brand than price.
That said, Amazon doesn’t take the lion’s share of private-label conversions—at least for the time being. Amazon's biggest private-label category, ranked by conversions, is electronics (45%), making up nearly half of its total. Home (16%), office (14%) and pets (5%) take smaller pieces of the pie. When looking at Amazon's private labels compared with Macy's, Target and Walmart, Amazon takes a 61% share, vs. 39% for those other three retailers combined. However, when you remove electronics, Amazon's share shrinks to 26%.
There is no official record or count of Amazon's private labels, but in March 2018, L2 reported that Amazon had 80 private labels, 86% of which were in the apparel, shoes and jewelry category. Health and household (5%) and home and kitchen (4%) were a distant second and third. This signals Amazon's continued intent to become a go-to source for online fashion, yet at least in Q1 2018, the sales weren't there yet.

According to a February 2018 Coresight Research assessment of Amazon Fashion, products from Amazon's private apparel labels only made up 0.1% of the clothing sold on the site. This reflects the long tail of brands on Amazon—the 30 that are most listed only account for 30% of the total—and also shows that there is room for private-label growth on the site. The most listed private label was Lark & Ro, making up more than half (54%) of Amazon's private-label listings. Women's dresses and blazers/suiting were the top two items listed under the Lark & Ro umbrella.