Vinted
Vinted's product-market fit did not arrive when users started buying. It arrived when they started selling without anyone asking them to.
In the early years, Vinted saw decent buyer retention but low seller retention — the classic marketplace problem: without supply, there is no demand. The breakthrough came from a counterintuitive decision: eliminating seller commissions entirely in 2012.
The effect was immediate and more intense than planned: sellers started sharing their profiles on social media, inviting friends, building mini-communities around their wardrobes. NPS climbed. Seller retention tripled in six months.
The clearest product-market fit signal was not transaction volume — it was spontaneous behaviour: people photographing their clothes on weekends, writing detailed descriptions, responding to messages within minutes. They weren't using Vinted because they had been acquired — they were using Vinted because it had become part of a routine.
This led Vinted to reformulate its revenue model: instead of seller commissions, it introduced optional buyer services (purchase protection, listing visibility). Product-market fit guided the business model, not the reverse.
Product-market fit is not measured only by growth metrics — it is recognised in spontaneous user behaviour you did not ask for, predict or incentivise.