Thrifting is back, though this time it has a tech spin on it.

An entirely new generation has discovered the pleasures of digging through other people’s discarded clothes in the hopes of finding the perfect piece. Hoping to cash in on the trend, companies have been embracing resale platforms, allowing them to capture some residual value while polishing their sustainability bona fides.

If it sounds too good to be true, it is for now, at least. Brand-owned resale still has a few kinks to work out if it’s going to transform retail.

Few companies have embraced resale as much as Patagonia, the outdoor gear supplier. Its Worn Wear program, which began as a used clothing section in its retail stores, is now a full e-commerce site that offers discounts on items with plenty of life in them. For brand aficionados, it also gives them access to back catalog items that are no longer available. It’s been a decade-long experiment that teases what a future circular economy might look like.

For companies like Patagonia, brand-owned resale is appealing for several reasons. The privately held company’s clothing has a reputation for being “buy it for life,” and its items tend to last for years, even decades. Plus, for a company that has staked its name on sustainability, selling used clothing is a logical extension of the brand.

For other companies, even if sustainability isn’t a key differentiator, brand-owned resale sites can help capture some of the value that would otherwise go to secondhand markets like eBay, Poshmark, Mercari and others.

To fill Worn Wear’s virtual shelves, Patagonia pays people for their old clothing. Not as much as they might get if they were to sell them directly on other resale sites, but it promises to be a simpler process: either drop off the clothes at a Patagonia retail store or mail them in. The company’s partner, Trove, handles the rest.

Once an item arrives at Trove’s warehouse in California, a team of workers inspects and photographs it. It also compares the item ID against a database it maintains to determine whether the piece is authentic. Items that can’t be identified (maybe the item ID is unreadable), the company employs computer vision to narrow the possibilities. The workers log descriptions of each item’s condition so that once they appear on the resale site, which Trove also manages, customers have a decent idea of what they’re buying. Since each item that winds its way through Trove’s warehouse has different wear patterns, they all receive unique SKUs. Partners can monitor their resale platform’s performance through dashboards, reports and CRM integrations.

Trove has ridden the resale wave, raising over $150 million total, including an early-stage investment from Tin Shed Ventures, Patagonia’s venture capital fund. It’s not the only resale platform that works directly with brands, but it’s broadly considered a leader. Recently, though, Trove appears to have stumbled. Its Series E round, which closed in July, added another $30 million to its coffers but also cut its valuation in half, according to PitchBook. Still, the resale company has managed to attract a dozen clothing and outdoor gear companies to its platform, including not just Patagonia but also REI, Levi’s, Lululemon, Allbirds and others.