E-commerce company eBay will launch a mobile ad network by the end of the year, allowing advertisers to target the 4.6 million daily users who spend an average of 150 minutes on the eBay app per month. Because eBay account holders have a single login assigned across their various mobile devices, the ad network collects data about user activity, including shopping habits. Triad Retail Media has partnered with eBay to place the ads across a variety of smartphone and tablet platforms.

The online retailer is pushing the ad platform by emphasizing its “highly engaged” mobile users. The company claims that its mobile users spend three times as much time on the eBay app than they do on the nearest competitor’s app.

In 2013, eBay customers purchased about $20 billion in gross merchandise volume on mobile. That’s about 40 percent of eBay’s sales that year.

The ad network is expected to become a new and growing source of revenue for eBay and Triad. Research firm eMarketer predicts that worldwide spending on mobile advertising will jump to $32.7 billion this year, compared to last year’s $17.7 billion. The firm also estimates that mobile advertising will account for 37 percent of U.S. marketers’ total spending.

This kind of potential is attracting other online retailers as well. According to The Wall Street Journal, “Advertising is an attractive market because it tends to generate much higher margins than the sale of goods, as on eBay, Amazon.com, and other sites.”

Amazon is also reportedly revamping its own ad network to possibly compete with the search-related marketing of Google’s AdWords.