Product-Market Fit describes the state in which a product serves a real need in a defined market so well that clear, organic demand emerges. It is the most important milestone for any new product or business model — and simultaneously the one most frequently skipped. Without Product-Market Fit, growth is burning money: marketing brings users who do not stay, and scaling only magnifies the problems.
The best-known test comes from Sean Ellis: if more than 40 percent of users say they would be “very disappointed” if the product disappeared tomorrow, Product-Market Fit is present. Below 40 percent, action is needed. In practice, PMF also shows through other signals: users recommend the product on their own, the retention curve flattens at a stable level, and demand exceeds the team’s capacity. Marc Andreessen described it pragmatically: you feel it when you have it — and if you have to ask, you do not have it yet.
The concept was popularized in 2007 by Marc Andreessen. The most common trap: teams that declare Product-Market Fit before they have robust data because the pressure to scale is great.