Gen Z Designers Made It Big on This App. Now They’re Graduating.

On Depop, most of her interactions with customers happened only when they wanted to buy something, Ms. Lopez said. But on Instagram, she said, she could share more personal moments from her life through features like Stories — which people use to post photos and videos that disappear after 24 hours — so “people get a feel of who I am and who they’re buying from.”

Ms. Lopez still spends more time on Depop, where she has 30,000 followers, compared with fewer than 1,000 on Instagram. Her best-selling item, a $58 mesh halter top with embroidered flowers, went viral on Depop this year, winning her shop adulation from customers in comments and reviews.

Other Gen Z designers are spending far less time on their Depop store these days. Desireé Zavala, 23, from Caguas, Puerto Rico, branched out to Instagram last year after sales for her Depop shop, Conscious Brat, sagged. (The shop’s name is a nod to Bratz dolls.)

Ms. Zavala said she now preferred Instagram, where tools such as Reels, which allows users to create short video montages, have let her ask customers for feedback, show off outfits and tease new items. She said she was not able to communicate with customers that way on Depop.

Depop “looks like social media, but it doesn’t feel like social media to me because I don’t feel like I can connect with anyone there, so it’s just strictly business,” she said.

Ms. Zavala has about 14,000 followers on both Instagram and Depop. While 90 percent of her sales come from Depop, her Instagram feed is livelier. She recently posted a photo of a red-and-black lace camisole, captioned “hOT GotH SumMer,” earning about 3,000 likes on Instagram and just 100 likes on Depop.