What does your Netflix viewing history reveal about you?

What’s your favorite Netflix show? And what does it say about you? That is a question that both Netflix and advertisers may be keen to answer.

Netflix is testing advertisements for original Netflix NFLX, +0.64%  content between episodes of other shows, a move that had some subscribers threatening to cancel the service. Netflix knows exactly how many times you’ve watched the latest season of “Queer Eye,” whether that’s your secret shame or your private pride. Those habits give the company an idea of what other shows viewers would like to watch and help Netflix make more accurate recommendations. However, data analysts say they also help predict what brands people buy when they’ve finished bingeing their favorite shows.

Viewing habits give Netflix an idea of what other shows viewers would like to watch, but data analysts say they can also help predict what brands people buy when they’ve finished bingeing.

Do you like to watch re-runs of “Friends”? You’re probably not a Kenneth Cole fan. Are you a fan of “Orange is the New Black?” Then you may not be a big user of Crest toothpaste. They seem like random conclusions, but data analytics companies are attempting to figure out what kinds of brands viewers of certain Netflix shows gravitate towards. For Netflix, which arguably has more granular data on people’s viewing habits than network television — including how, when and for how long they watch a show — that information can be very valuable.

Browsing history can paint a detailed picture of viewers than watching shows on cable and network TV, according to Jumpshot, a San Francisco marketing and analytics company that develops these kinds of user profiles for a number of companies (but not Netflix itself). MarketWatch gave Jumpshot some popular Netflix shows and the company used its algorithms to determine what brands people buy and search for online. “We take a broader view of your history,” said Deren Baker, chief executive officer of Jumpshot.

The company said it has an opt-in panel of 100 million devices where users share their browsing behavior. They aggregate and analyze this anonymous data to provide insights about online behavior to their customers. Cookies help the website keep track of the user’s movement within the site. When cookies are collected across different websites, it helps create a larger picture of a user’s browsing habits. Coupled with viewing habits, tracking users’ tastes in shows and products is getting even more complex.

This algorithm helps Baker to make broad inferences about Netflix viewers and their search habits that his company then sells to clients. Viewers of “Queer Eye,” the makeover show hosted by five gay men, were almost four times more likely to buy laptop bags from Mosiso. Viewers of “Orange is the New Black,” the women’s prison-based black comedy, and “The Crown,” the series chronicling the reign of Queen Elizabeth II, were three times more likely to buy Kenneth Cole Reaction products, and viewers of “The Crown” and “Queer Eye” were twice as likely to buy for Neutrogena JNJ, +0.33%  products, Jumpshot found.

Viewers of ’Queer Eye,’ the makeover show hosted by five gay men, were almost four times more likely to purchase or search for laptop bags from Mosiso, the Jumpshot analysis found.

A Netflix spokeswoman told MarketWatch the company is only promoting its own content between shows, not creating commercials for other products. “At Netflix, we conduct hundreds of tests every year so we can better understand what helps members more easily find something great to watch,” she said. Video previews help subscribers make choices from a selection of videos based on their viewing history, she added. “We have been experimenting even more with video based on personalized recommendations for shows and movies on the service or coming shortly.”

Of course, marketers have long cross-referenced viewing habits and shopping and lifestyle habits. Older viewers who watch a certain cable news show may be more likely to buy certain medicines, for example, or might be interested in releasing equity on their home or consolidating their loans. People who watch the mockumentary series “Modern Family” on ABC DIS, +0.64%  have a median annual income of $81,100 while people who watch Bob’s Burgers, an animated sitcom about a family that owns a hamburger restaurant, earn a median annual income of $48,800.

But Netflix knows exactly what you shows you watch, and even if you went back and watched them again. Last year, the company tweeted, “To the 53 people who’ve watched A Christmas Prince every day for the past 18 days: Who hurt you?” Some privacy advocates were alarmed at the seemingly lighthearted revelation about customers’ habits. After backlash about the company “spying” on its paying users, it noted in a follow-up tweet that the original joke tweet was based on aggregated, anonymous user data. The company, the Netflix spokeswoman said, has no immediate plans to introduce advertisements.

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