Survey results released on Monday showed that 45 million people, or 47 percent of all smartphone owners, used mobile apps in the Nielsen-defined Shopping/Commerce category in June. Nielsen projected those findings from a survey of 5,000 iOS and Android users who agreed to have Nielsen install app-use tracking software on their phones. It was Nielsen's first study of a particular category of mobile app.

The results don't mean that consumers are necessarily buying things on their phones. In fact, most of the top 10 apps in the category just help users find deals or organize their shopping. Nielsen's software doesn't look into users' mobile purchases.

The biggest mobile shopping apps are familiar names from online and retail shopping: eBay Mobile was most popular in June, with an estimated 13.2 million unique users, followed by Amazon Mobile, with 12.1 million. Drugstore chain Walgreens came in sixth place and big-box retailer Target was seventh.

But consumers frequently look to their mobile phones for other shopping-related functions. Online discount company Groupon's app was the third most popular app in the category in June, used by an estimated 11.9 million unique customers. Next up was ShopKick, which just for going to brick-and-mortar stores and for scanning certain products. It was used by nearly 6.5 million people in June, according to Nielsen. Other popular shopping apps included RedLaser, a barcode scanning tool, the shopping-list app Out of Milk, and SavingStar Grocery eCoupons.

Smartphone owners who used shopping apps in June turned to them 17 times during the month, on average, but the amount of time they spent with those apps varied widely. The average user of eBay Mobile spent just over one hour with the app in June, while Amazon users spent less than 19 minutes for the month. Shopkick topped the list with an average use time of three hours, 19 minutes, possibly because the app rewards users for visiting stores and has to be on to record their entry.