At this point in the story, you may be wondering: What even is a Top Brand? Are Top Brands selected by humans? Or is the metric controlled by an algorithm? Amazon, for its part, says the Top Brand badge simply highlights brands that customers love, but did not go into any further detail about how that's determined.

WIRED reached out to four Amazon experts to ask about the logic behind the preexisting Top Brands filter, including two former employees, and they each had different explanations. Fred Dimyan, the CEO of Potoo Solutions, a firm that consultants with ecommerce companies, says Amazon takes two factors into consideration when awarding the honor: the amount of products a brand sells and how many different products they offer in the first place. In other words, companies that make a narrow range of goods, but sell a lot of them, are likely to be Top Brands. Dave Bryant, an Amazon seller and blogger, thinks the distinction might be related to customers’ overall purchase satisfaction, which can include metrics like how often people returned items.

Louise Matsakis covers Amazon, internet law, and online culture for WIRED.

James Thomson, a former Amazon employee and a partner at Buy Box Experts, a firm that consults with independent Amazon sellers, says Top Brands likely have high sales volumes and high conversion rates, meaning a lot of people who look at their product listings ultimately choose to buy from them. Chris McCabe, another former Amazon employee who now consults with Amazon sellers at eCommerceChris.com, says Top Brands are the highest revenue-earning items in a certain category. Every expert agreed that “Top Brand” is not a promotional title companies can pay to display on their Amazon product listings.

At least anecdotally, Top Brands look to encompass household names you might find in a mall, like Steve Madden, Oakley, Under Armour, and IZOD. That might be the point: to flag the names you’re already familiar with from shopping in brick-and-mortar stores, so it’s easier to purchase something quickly from a trusted company. “I wouldn’t be surprised if the idea is to make this function like being verified on social platforms,” says Juozas Kaziukénas, founder of the ecommerce intelligence firm Marketplace Pulse, who first alerted WIRED to the Top Brand badge. But there are also lots of unknown companies with the Top Brand distinction, and every one of Amazon’s in-house labels appears to be designated a Top Brand, too.

After WIRED reached out to Amazon for this story, something strange happened. Many of the Top Brand badges that had been present in search results WIRED conducted disappeared, including in an incognito browsing window on several different computers, browsers, and phones. Amazon says because the feature is a test, it may not always be visible.

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US lawmakers have begun scrutinizing how Amazon evaluates the goods for sale in its sprawling marketplace using signals like Top Brand. On Monday, Senator Bob Menendez and Senator Richard Blumenthal, both Democrats, sent a letter to Amazon CEO Jeff Bezos asking for a “detailed explanation” about how the Amazon’s Choice badge is awarded, after a Buzzfeed investigation found it was sometimes given to what appeared to poor-quality items. Democratic presidential candidate and Massachusetts senator Elizabeth Warren has also expressed concern that Amazon may favor items from its own house brands over those from competitors. And the Department of Justice and Federal Trade Commission each recently announced they are looking at the business practices of online marketplaces, including Amazon specifically.

In a statement, a spokesperson for Amazon didn’t respond directly to the senators’ letter. The company instead highlighted its efforts to detect fake product reviews, and said it believes that 90 percent of inauthentic reviews are computer-generated.

Opaque features like “Top Brand” serve as a reminder that Amazon isn’t a traditional retailer, despite the fact that it often wants to look like one to consumers. It’s an enormous marketplace where millions of independent merchants from around the world sell their goods. Amazon needs not just to combat bad actors but also steer customers toward the brands it knows they’re likely to be happy with, or risk them getting overwhelmed and going somewhere else. The hard part for Amazon, like every online platform, is figuring out how to manage the chaos without taking full responsibility for the consequences of its management choices.

Is there something about Amazon you think we should know? Contact the author at louise_matsakis@wired.com or via Signal at 347-966-3806.

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