This is a translation of "The Real Product Market Fit" by Michael Seibel, CEO of Y Combinator. The original article is here.
Most founders treat product-market fit as a binary — you either have it or you don't. But that framing misses what's really happening. Product-market fit exists on a spectrum, and understanding where you sit on that spectrum is essential for knowing what to do next.
What product-market fit actually feels like
The most reliable signal of product-market fit is retention. Are people coming back and using your product week after week? Are they telling others about it without being asked?
The opposite signals are also clear. If people try your product and don't come back, that's a strong sign you don't have it. If you have to constantly push customers to keep using it, or if churn is high, you don't have it.
The pre-PMF stage
Before finding product-market fit, your entire job is to find it. This sounds obvious, but founders constantly get distracted by things that feel productive — hiring, fundraising, press — while avoiding the hard work of talking to users and iterating on the product.
The key question to ask yourself: "Are there people who would be genuinely disappointed if my product disappeared tomorrow?" If you can't find even a small group of people who feel that way, you haven't found product-market fit.
The PMF spectrum
Product-market fit isn't a single moment. It's a continuous process of deepening the fit between your product and your users' needs.
Weak PMF: You have users who return, but inconsistently. They like the product but it's not essential to them. Growth is flat or slow.
Moderate PMF: You have a core group of highly engaged users. Word of mouth is beginning to work. Retention curves are flattening at a meaningful level.
Strong PMF: Retention is strong across segments. Growth is happening organically. You're struggling to keep up with demand rather than struggling to generate it.
How to find PMF
The path to product-market fit runs through users — specifically, through understanding them more deeply than they understand themselves.
Talk to users constantly. Not just when you're building features, but always. The goal is to develop such a deep understanding of your users' problems that you can anticipate what they need before they can articulate it.
Be willing to change your product dramatically. Many founders build something they personally believe in and then try to convince users to agree. The better approach is to let what you learn from users reshape your product fundamentally.
PMF and market choice
One thing founders underestimate: the market you're in matters enormously. A great product in a bad market will struggle. A decent product in a great market can succeed.
When evaluating whether you have product-market fit, always ask: is this market large enough? Even if you have strong retention and love from users, if the total addressable market is small, you'll hit a ceiling quickly.
After finding PMF
Once you have genuine product-market fit, the game changes. Before PMF, optimize for learning. After PMF, optimize for growth.
But beware: product-market fit is fragile. Markets change. Competitors enter. User needs evolve. A product that fits well today may not fit well in two years. Maintaining PMF requires continuous attention to users and willingness to keep evolving.
The best founders never stop treating product-market fit as something to find and maintain — even after their company has grown large.
