In December, Ellicia Chiu and Cher Su had just a few boxes in tow when they moved into a walk-up apartment in New York’s Lower East Side neighborhood. Before their move, from Los Angeles, the two friends knew that they would need to furnish their new apartment with small kitchen appliances, décor and furniture. But instead of purchasing new items, they knew it would be more affordable to find secondhand items on Facebook Marketplace, the social network’s buy-and-sell service.

“I only use Facebook for Marketplace,” said Ms. Chiu, 24, who added that she spent most of her social time on TikTok and Instagram, which is owned by Meta, Facebook’s parent company.

For many 20-somethings who don’t have a lot of disposable income, Marketplace is a place to get deals on items they wouldn’t normally be able to afford.

“As someone who’s in their young 20s, I want to have nicer things but I don’t have the financial means to get there yet,” said Ms. Chiu, who added that she preferred Marketplace over other sites because its interface was easy to use, making it easier to find deals on furniture.

Over the past decade, Facebook has declined in popularity with Gen Z as a social site, a 2022 Pew Research Center survey found. Instead, younger people are spending more of their social time on Instagram, TikTok and Snapchat.