How do retailers know what will sell out? They check TikTok

Shoppers are no longer turning to retailers to figure out what products to buy, how to wear their hair and what makeup styles are trending — they are figuring it out for themselves on TikTok. That leaves retailers chasing the trends instead of making them.

Much of the conversation on what to buy is driven by shoppers on the once-niche social media app designed to share dance trends.

“A few years ago, TikTok was just this teen app with 35 million users where you thought, 'Eh, I don't know,'” said Debra Williamson, a social media analyst with eMarketer. “It will have 79 million users in the U.S. this year, which is pretty substantial growth.”

But over the course of the pandemic, the app has grown by 87 percent, far outpacing Reddit at 25 percent and Pinterest at 8 percent, Williamson said. While YouTube still takes the top spot for in-app spending, TikTok comes in second, according to a March report from the app analysis firm App Annie. Overall, consumers across the world spent $32 billion in just the first three months of 2021 on in-app purchases, the company reported.

Consumers across the world spent $32 billion shopping on apps in just the first three months of this year.

With a mainly young audience — but a growing share of adult users — companies are finding unexpected trends leading to skyrocketing sales and sold out shelves. A product going viral on TikTok is just like a dance or song going viral — it starts with a few trendy creators showing off a hot commodity like LED light strips illuminating their bedrooms or driving through Starbucks to order a complicated personalized “appucino” which sends followers scrambling for the same items. Dozens of companies briefly sold out of product at the height of their virality, including a Stardrops cleaning product called The Pink Stuff, a line of butt-lifting leggings on Amazon and lash-lengthening mascara from Maybelline.

After a ravaging year for the retail industry during the pandemic shutdowns, TikTok has driven sales at some of the country’s most iconic, but struggling, companies. Gap, which has closed more than 100 stores since the beginning of last year and has struggled to gain relevance among younger shoppers, saw some of its products unexpectedly take off on TikTok.

Gap’s "high-rise cheeky straight" jeans and "sky-high straight" jeans saw sales surge this year as TikTok helped spur a frenzy for loose-fit “mom jeans.” Gap saw a 200 percent increase in the number of cheeky straight jeans sold online within just a day, Mary Alderete, global head of Gap marketing, told NBC News in an emailed statement.

Gen Z's affinity for nostalgic styles from the 90s and early aughts has also helped the brand. Earlier this year, a basic brown Gap hoodie initially sold in the 2000s took off on TikTok and Instagram where users posted videos of themselves wearing the classic sweatshirt. The hashtag #gaphoodie has gained more than 5 million views on TikTok and helped rack up the price to as much as $300 on resale sites like Depop and Grailed.A basic brown Gap hoodie from the 2000s gained more than 5 million views on TikTok and helped rack up the price to as much as $300 on resale sites.GAP

“While virality comes from the social community and can’t be forced, based on original consumer response, we’re excited,” Alderete said.

Following the hoodie’s success, Gap is this week set to launch its own campaign with TikTok, partnering with the app and several creators — including Vienna Skye, Brittani Lancaster and Larray — to let users pick the new color for a revived version of the viral sweatshirt through crowdsourcing.

Advertising on TikTok is not the same as running a commercial on TV. Typically, brands develop trends with a select group of creators such as the song “Eyes, lips, face” launched by e.l.f. Cosmetics, which went viral last year with few users realizing it was a campaign.

Amy Simon, a spokesperson for the online clothing retailer Pretty Little Thing, told NBC News that the company is constantly monitoring trends on TikTok. Several of the company’s clothing pieces have gone viral including a corset and skirt ensemble and a top that one user wore backwards that sold out online after the company boosted the video on its own TikTok page.

The explosion of shopping interest on TikTok has also created a thriving subgenre of shopping haul creators who share their finds from thrift stores or dollar stores. Aprill Dobrowski, 34, of Pennsylvania, who makes “haul” videos of her finds from the discount store Five Below, told NBC News that people are drawn to her videos because she tests products to keep other shoppers from wasting their time driving to the store for a particular item.

In one video, she buys five lamps from Five Below only to discover when she got home that four of them popped and sparked out as soon as she plugged them in.

TikTok has raised estimates among some retailers for how quickly shoppers will return to stores and help drive economic recovery.

“For that one, I actually just wanted to warn people because I think in my opinion it could have been a fire hazard and these things are still on the shelves,” she said.

Five Below did not respond to a request for comment from NBC News.

With inflation raising prices and a bifurcated economy still squeezing some shoppers' wallets, TikTok has raised estimates among some retailers for how quickly shoppers will return to stores and help drive the economy toward recovery.

“Engagement with social media platforms like TikTok are bringing new life to the color cosmetic category, engaging younger audiences, driving trends and reinvigorating trial and usage,” David Kimbell, CEO of Ulta Beauty, told investors in May. “These drivers, combined with an expanded pipeline of newness expected in the second half of 2021, increase our optimism about the pace of recovery of the makeup category this year.”

With the pace of TikTok’s growth and influence on store shelves, retailers and their marketing teams are taking notice.

“Most advertisers want to reach people where they’re sharing who they want to be and what they want to look like,” Williamson said. “That’s always a good environment to push your advertising.”