It isn’t easy competing with Amazon.com Inc.

The e-commerce giant isn’t shy about flexing its marketing muscles to grab a larger share of the e-commerce market. Amazon boosted its marketing budget 37.6% last year to $7.233 billion—that’s 16% more than Macy’s Inc.’s $6.210 billion 2015 online sales. That aggressive approach helped Amazon garner what Slice Intelligence estimates was 43% of all U.S. online retail sales last year.

Amazon is hardly alone in boosting its marketing spend; most retailers, 63.5%, are boosting their digital ad spending this year, according to an Internet Retailer survey conducted in August. But the spending increases most merchants have planned pale in comparison to Amazon’s. 54.2% of retailers plan to boost their marketing budgets no more than 25% more this year. Amazon’s massive scale—its 2016 revenue totaled $136.0 billion—means that even some of its larger competitors like Overstock.com Inc. have to pick their marketing spots carefully.

“We’re a pure play that’s striving to be profitable,” says J.P. Knab, Overstock’s senior vice president of marketing. “Our marketing algorithms try to create bottom-line dollars, which means we need to be intelligent in our targeting. We can’t just try to seek impressions in front of everyone.”

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For Overstock, which boosted its marketing budget 18.7% last year to $147.9 million from $124.5 million, that means using the propriety data it gathers about its customers—both online sales information and behavioral information collected via a “fingerprint” that enables it to track them across devices—to predict how a shopper will respond to a particular product featured in an ad. While Overstock keeps details related to its tracking close to the vest, Knab says the program helps the retailer’s search, display, email and social media marketing strategies, each of which aim to promote products based on shoppers’ interests and to reach consumers wherever they’re looking, which is increasingly on a smartphone—and to a lesser extent tablets.

Overstock isn’t alone in the fact that it boosted its spending on online marketing last year. In fact, 11 top publicly traded web-only retailers, for the first nine months of the year, boosted their collective spend on marketing by 32.2%, to $6.37 billion from $4.82 billion.

Overstock’s efforts are working, as it generated a $12.5 million net income last year, a 420.8% gain from $2.4 million in 2015, while also earning the No. 8 spot in Internet Retailer’s ranking of the 50 best e-retail marketers. The ranking is based on an exclusive algorithm that weighs dozens of metrics across four digital marketing channels—email, paid search, organic search and social media—to determine the retailers that are most efficiently and effectively driving consumers to their sites and apps to buy (For the sake of comparison, Amazon is No. 4). Overstock and the other retailers ranked in the Best Digital Marketers in E-Commerce are successfully leveraging the massive trove of information they know about their customers to tailor their messages to an individual shopper’s interests—and they’re doing so across email, paid search, natural search and social media.

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