Retailers that have put in the work to developing a mobile app have to work just as hard to get shoppers to use their app and spend time in it.

Among top online retailers and marketplaces, more than 1 million shoppers visited their app each month in 2018, according to comScore Inc. data. Amazon.com Inc. (No. 1 in the Internet Retailer 2018 Top 500) generated the most monthly app visitors in 2018, at more than 100 million, with the next-closest retailer, Walmart Inc. (No. 3), at 42 million unique app visitors. For each retailer, comScore’s data includes all of that’s retailer’s owned brands. For example, Amazon’s data includes mobile web and app data from its Zappos brand.

Here’s how top online merchants’ apps stack up:

Amazon not only has the most app visitors, but Amazon app shoppers spend exceedingly more time in the Amazon app compared with other top retailers. On average per month in 2018, consumers spent 12.84 billion minutes in Amazon’s app. Internet Retailer eliminated Amazon from the following chart to better compare the other merchants.

It’s notable that even though eBay Inc. attracts fewer unique visitors to its app each month compared with Walmart, eBay’s shopper are spending more time in its app compared with Walmart shoppers.

Even more interesting is comparing a retailer’s app shoppers with its mobile web shoppers. All of the retailers generated more unique mobile web visitors in a month than unique mobile app visitors, according to comScore data. However, when comparing how much mobile time is spent with retailers, a retailer’s app shoppers, although fewer, cumulatively spent more time with the retailer than mobile web shoppers.

Nordstrom Inc. (No. 16) is a good illustration of this. Of all consumers who visit Nordstrom on a smartphone on average per month, only 8% do so in the app. However, those shoppers generate 81% of the mobile minutes Nordstrom generates per month.