In less than a decade, Vestiaire Collective has become the go-to for online sales of second-hand fashion.

There was a time when eBay was pretty much the only viable re-commerce platform around. But what if, in the years before 2009, you were a fashion lover who wanted to buy or sell top-quality designer clothing or accessories? Aside from eBay and its notorious unreliability for high-end goods, there was the inconvenience of buying from individual bloggers or (millennial shocker!) brick-and-mortar second-hand shops.

For Fanny Moizant, one of the six founders of online designer resale boutique Vestiaire Collective, it was that inconvenience of buying from bloggers that nudged her to start the online luxury consignment app, which currently has more than seven million users. "The lightbulb moment for us was that the girls with fashion blogs couldn't maintain wearing new outfits every day and had to sell what they wore on their blogs," explains the French tech entrepreneur, who moved from Paris to London in 2013, then to Hong Kong last year. "I was personally interested in buying, but the correspondence and payment was very inconvenient. I had to send an email, then a cheque or money transfer… It was a pain. So I decided to bring fashion people onto one platform based on trust, with a smooth trading process."

Moizant wanted the opposite of a timed bidding system like eBay's. The app has a suggested selling price, but the final price is determined by the community after discussions (aka bargaining) between buyers and sellers. Bidding is market-driven, where people can strike a deal as soon as both parties agree on a price. The app makes buying and selling easy – members don't have to keep checking back like auctions or eBay. To emphasise how fast buyers react to desirable stock, Moizant firmly says, "A good product with a good price goes without bidding." Vestiaire Collective collects anywhere from 25% to 40% commission on sales.

In terms of positioning and perception, Vestiaire Collective is the most luxurious and fashion-forward of the re-commerce sites. There's something for everyone, from Zara ("super-special exception") to exclusive Supreme drops, along with classics like Chanel, Louis Vuitton, Gucci and Hermès. The app currently has more than a million products online and accepts 35,000 new consignments every week. "This isn't just a luxury website; it's for everyone who loves fashion," explains Moizant, who's wearing a second-hand striped Chanel T-shirt and current-season Celine palazzos, which she will be selling online soon. "We want to show a panorama of fashion that reflects contemporary style of mixing high and low. Who wears head-to-toe Hermès? Some members are from the industry or in media, and many more from other careers or lifestyles – but the common thread among all our users is their passion for fashion."

Moizant and her partners have also identified a changing attitude towards the consumption, value and ownership of fashion items. Aside from being a trading platform, the app serves a new generation who values sharing and usage more than possession, who is addicted to newness, who doesn't own a lot for various reasons, yet who has one eye on value and another on style. Vestiaire Collective ran a survey among its members and discovered that "buyers and sellers have a value mentality more accurate than ever," explains Moizant. "When they buy something [at retail], they have a resale value in mind. Investment dressing used to be cost-per-wear, but now it's 'How much do I recoup if I spend $1,000?'"

She continues, "Vestiaire Collective facilitates a new and inspiring way of consuming fashion. You want new things, but you have to let go of others. We are closing this circle. This is not just a way of recycling, but slowing the pace of consumption, because it is going very fast – way too fast."

Vestiaire Collective remains a closely held private company. It has raised more than €100 million (including $20 million from Condé Nast in 2013); according to Moizant, funding was "never a problem."

Being French was never a problem either – and in fact, has proved to be a great advantage. Although 65% of the business is generated outside France, its homeland is still the single biggest buying-and-selling market.

"In this particular industry, a Parisian image gives undisputed credibility and heritage to any luxury brand," elaborates Moizant. "It's a good thing – and we are proud of our French DNA."

The company's next biggest markets are the UK, Germany and the US, with "developed Asia" (Hong Kong, Singapore and Australia) quickly gaining more market share. Moizant also claims that China, Korea and Japan have grown organically for the company without any PR or marketing effort. Welcome to the future, where fashion is now at your fingertips.

Fanny Moizant's Top Selling Tips

1. Use the app and read instructions carefully. Detailed photos and presentation are very important.

2. Don't try to hide defects, because our curation team will definitely see them when they receive your goods for vetting.

3. Put yourself in the buyer's shoes and ask yourself how much you would pay for your item. If you do, you'll understand rejection (if any) and become a successful seller.