Things bought on impulse but never used, outdated items and valuable classics – they've all become salable in China. China's used goods markets are thriving as more young Chinese cast off their parents' and grandparents' automatic rejection of used stuff, and embrace online platforms that offer goods at cheaper prices.

Submitting the photos, adding the labels and descriptions, and of course, setting the price – within five minutes, Song Yanru has her baby carriage for sale on Xianyu, Alibaba's online store for used goods. During the past four years, she has sold 11 items on the platform, and made 1,000 yuan (about 146 U.S. dollars).

"The value of household goods drops a lot once they've been used, so I usually set the price at half of what I paid for them. And now the e-commerce platforms are discounting pretty heavily, some as low as 30 percent or 40 percent. Even some products that I haven't used have prices set at less than half the original," said Song Yanru.

Still, that's money she wouldn't otherwise have. Song usually sells furniture and baby care products, with most of the items moving within 10 days. Alibaba's Xianyu now has nearly 100 million active users a month.

"Consumers between 20 and 25 focus more on brands and cost-effectiveness. They prefer brand-new clothes from Zara at half price, or a Kindle at 60 or 70 percent off. Five million shoppers between 10 and 30 years old log in our platform every day to look for things like blind boxes, derivatives and sports shoes. Our baby care market sells around 4 million paper diapers a year," said Wang Chengyuan, senior product professional at Xianyu.

At one time or another, more than 200 million people have bought or sold something on the site, which in the last six years has listed almost 2 billion items for sale.

Selling or buying second-hand stuff is not just limited to online platforms. The business is growing so quickly that there are now offline boutiques specializing in selling second-hand fashion goods. And buying vintage products has even become a new fashion trend.

This store in Shanghai's downtown Xuhui district has been selling vintage clothes, jewelry and handbags for 11 years. Business is picking up.

"Many customers have gotten to know us from social media platforms like Xiaohongshu and Meituan Dianping, so we're getting more customers now. And for vintage products, it's better to sell offline because consumers have to try the clothes on to judge the style and the cloth," said Lolo, founder of Lolo Love Vintage.

Lolo's most popular items are clothes from the 1980s and 90s, and full skirts from the 1950s, which go for 1,000 yuan. She says she has a list of 200 shoppers who have spent more than 20,000 yuan each on her vintage deals. With more and more Chinese shoppers searching for a good deal – or for that special classic fashion item – the new second-hand shops are here to stay. The China Center for Internet Economy Research predicts that transactions for used goods in China are expected to exceed 1 trillion yuan this year.