Phia, A Shopping App From Two Stanford Grads, Launches Amid Resale Boom

Forbes

24-04-2025

The U.S. secondhand apparel market is expected to reach $74 billion by 2029. (Photo by Neil ... More Godwin/Future Publishing via Getty Images)
Secondhand apparel shopping has steadily grown to become a significant channel for consumers, and Phia, a new app and browser extension, is determined to help customers navigate the booming space and what's worth purchasing new or not.
Phia works like 'the Google Flights for fashion,' said Sophia Kianni, co-CEO, helping shoppers discern whether they should buy an item new or secondhand based on aggregate resale data. Phia displays a graph showing the average prices for first-time purchases and second-hand purchases of a particular item. Suppose a white dress from a specific designer or store is selling for $200, for example, but the comparative resale value is $150. In that case, consumers might consider finding something secondhand or feel confident in their purchase.
Phia is available for free both on Google Chrome and as an iOS app, where a user can add it and enable as a Safari extension. While browsing on Safari, users tap the 'Should I Buy This?' button on the Phia browser extension to get an instant price check, based on Phia's database of 250 million secondhand items. It can be used on over 40,000 shopping sites. Phia earns revenue through affiliate links when someone completes a purchase.
Kianni's background is as a climate activist, and founded Climate Cardinals, a nonprofit offering climate change information in multiple languages, and is an advisor to the United Nations. She was also listed in Forbes' 30 Under 30 in 2023. Her co-founder and Co-CEO Pheobe Gates is the youngest daughter of Microsoft founder Bill Gates and his ex-wife, Melinda French Gates, and has publicly advocated for women's rights and reproductive health.
'The problem that we hit on time and time again was that we both loved secondhand shopping, but found it so difficult to compare across all of the different websites, and to know whether or not we were getting the best price or the best quality among what was out there,' said Kianni.
With the secondhand market growing in popularity, it's reasonable to suspect that customers consider the resale value when making a purchase. In 2019, resale platform Rebag created a tool to evaluate handbag resale prices, which it compared to the Kelley Blue Book, a nearly century-old vehicle valuation service. And brands themselves have sometimes embraced resale value as a marketing narrative to offer comfort to customers when considering a purchase. In 2023, Telfar, at the time, featured a link to Rebag's 2022 report on resale value on the brand's online product pages.
According to the resale market ThredUp, in its annual market report released in March, the U.S. secondhand apparel market grew 14% in 2024, marking its strongest annual growth since 2021. Overall, the U.S. secondhand apparel market is expected to reach $74 billion by 2029.
'People don't care about the resale value itself. What they care about is feeling justified in their purchase and knowing whether they should buy this item new, or should they buy it secondhand,' said Gates.
Kianni, left, and Gates, right, met as roommates while at Stanford. At the time, Kianni pursued ... More pre-law while Gates studied pre-med.
The idea for Phia emerged while the two were roommates at Stanford, sharing their experiences of shopping online and trying to find the same item sold by a retailer on second-hand sites. While Gates studied pre-med and Kianni planned to follow a legal career, but an entrepreneurship class persuaded them to eventually create the idea for Phia.
'It wasn't until we got in this ecosystem of learning about startups, seeing other kids building companies [at Stanford], that Sophia and I thought 'Oh, wow, this actually could be a full-fledged career path,'" said Gates.
The first iteration of Phia was a Google Chrome browser extension that showed someone a second-hand version of a product as they shopped on a website. Browser extensions like Beni and Faircado work similarly.
Notably, Phia launches at a time when secondhand shopping is poised for a greater boom than it has had to date due to potential tariffs. According to ThredUp, 59% of consumers say that if new government policies around tariffs and trade make apparel more expensive, they will seek more affordable options, like secondhand. Consumers across all ages plan to spend 34% of their apparel budget on secondhand in the next 12 months.
As they launch and scale Phia, Gates and Kianni plan to share those experiences on their new co-hosted podcast, 'The Burnouts,' while also conversing with like-minded entrepreneurs and sharing their journeys of starting and scaling businesses. Recent guests have included Kris Jenner, who is also an investor in Phia, and social media financial planner Haley Sacks, known as Mrs. Dow Jones. 'The Burnouts' premiered in early April as part of the Unwell Network, founded by Alexandra Cooper, the host of the 'Call Her Daddy' podcast.
Discussing the trials and tribulations of being an entrepreneur is an emerging podcast narrative, on the opposite end of the spectrum from early podcasts like Guy Raz's 'How I Built This,' which spotlight well-known and already successful companies and founders.
Notably, Meghan Markle-Sussex, the Duchess of Sussex, launched a podcast called 'Confessions of a Female Founder,' which also interweaves her story of building her lifestyle brand, As Ever, while discussing entrepreneurship with female guests.
'We're still in it and learning how to do things and making mistakes and coming up with new ideas [while] open sourcing knowledge that we're so lucky to [receive],' said Gates. 'That is important for us, and we want to pull back [the curtain] into Phia even more.'