The was just one problem: Amazon’s Data Protection Policy allows developers to use customer information only for tax and shipping purposes, not for advertising. Marusenko says he knew his software might be bending the rules but argues that it was an area Amazon didn’t seem to enforce—not to mention that thousands of sellers were requesting these kinds of features. “I was trying to find this balance on what Amazon wants and what Amazon sellers want,” Marusenko says. “There’s a lot of things Amazon doesn’t want sellers to do—but it’s very helpful for a lot of sellers.”

While Amazon MWS policies state that the company can audit developers to ensure compliance, it has relied heavily on developers to police themselves. “Originally, the MWS API was available to pretty much anyone,” says one Amazon developer, who requested anonymity because they feared retribution from the company.

But Amazon also appears to be exerting more control over outside developers since launching its Marketplace Appstore last year. For years, developers like Marusenko have been selling their software independently through their own websites. But soon they’ll be required to sell through Amazon, too: The company notified developers earlier this year that they must apply to list their apps in the Marketplace Appstore by September 30, according to an email reviewed by WIRED. (Sellers who develop apps for their own use and don’t offer them to anyone else appear to be exempt from this requirement.)

The app store, in theory, could give Amazon the ability to more closely monitor third-party apps and their data use, depending on how robust the application review is. The Marketplace Appstore could also earn Amazon revenue if it charged developers a percentage of sales similar to how Google and Apple’s stores operate. An Amazon spokesperson didn’t answer a question about whether the company planned to monetize its app store in the future.


The WIRED Guide to Online Shopping

In March, Marusenko began receiving emails from Amazon asking him to fill out a Developer Registration and Assessment form outlining what ZonTracker did, or risk losing access to Amazon data entirely. “At first I was really worried,” he says.

Marusenko wasn’t alone. Amazon’s seller forums are full of messages from confused and frustrated developers who abruptly lost access to its APIs throughout the spring and summer of 2019. Some posters have said they needed to wait months to hear back from Amazon about regaining entry. “They’re just basically like a bully; you don’t know how they’re going to behave,” one Amazon developer told WIRED.

Not everyone was blindsided by Amazon’s data crackdown. Liz Fickenscher, an industry liaison at the Amazon software firm eComEngine, says her company knew about the changes in advance because it’s part of Amazon’s Marketplace Developer Council, an invite-only program for a select group of developers. eComEngine was able to make the necessary adjustments, like updating a tool its clients use to send automated emails to customers. The tool had been pulling customers’ first names for a personalized greeting, but it stopped doing that in July. “Amazon has always been pretty protective of the data that they share,” Fickenscher says.

In the end, Marusenko says he told Amazon the truth about ZonTracker, and the company finally cut off his access to customers’ personal information last month. Before he lost the ability to pull that data, he found a way to adapt his business and survive. Marusenko says that ZonTracker now relies on aggregate data rather than individual customer information and that he successfully retained most of his paying clients. “I want Amazon sellers to be good about their data-privacy-protection policies, too,” he says.

A Larger Conversation

Amazon shoppers are unlikely to notice any changes as a result of Amazon’s MWS crackdown, but the move could help protect their privacy.