Poshmark is one of many companies racing to break into the United States’ nascent live shopping market, which is estimated to bring in $32 billion in sales this year, according to the retail consulting firm Coresight Research. Eying the live shopping market in China, which, by comparison, is projected to bring in $647 billion this year, American companies have for years poured money into the medium, where people buy and sell products in real time over video. But American consumers have yet to take to live shopping in the same way.

In 2016, the e-commerce giant Alibaba launched Taobao Live, popularizing live shopping in China. The livestream landscape is much more fragmented in the United States, but even as shoppers return to stores, retailers and large tech firms are betting that consumers will continue searching for, and purchasing, items on their phones. For platforms, live shopping promises more engagement, with consumers sometimes spending hours watching hosts sell items. For retailers, it’s another channel to sell their goods.

Alongside Poshmark, QVC’s parent company Qurate recently started Sune, a live shopping app targeting Gen Z. Last year, Walmart, YouTube and eBay added or expanded their live shopping features. For Prime Day, Amazon recruited celebrities like Kevin Hart to promote its Amazon Live platform. Shein was an early adopter when it began Shein Live in 2016 for U.S. shoppers. It started with just a few hundred viewers per episode and now averages “hundreds of thousands of viewers per episode,” said George Chiao, Shein’s U.S. president, in a statement.

“There’s just an insane level of excitement that we have seen,” said Manish Chandra, the chief executive of Poshmark, at the rooftop event. “In a very few short months, they’re proving that this form of live shopping works,” he added, referring to Posh Shows sellers like Ms. Lazovic.