A phrase that looms large in Silicon Valley: product-market fit. The startup founder’s North Star. The magic moment when the thing you made clicks into place with the world’s desire. It is whispered about in venture meetings, used to explain sudden growth spurts, and invoked as justification for rounds raised at irrational valuations. According to startup folklore, you know you have it when your product flies off the digital shelf, when growth becomes effortless, when users grab your tool and don’t let go.

This story has the neatness of a fable. It appeals to those who want the world to make sense. But most fables are lies told by optimists or survivors. And product-market fit, as popularly understood, is a lie of both.

The Historian’s Fallacy, Venture Edition

There’s a known pitfall called the historian’s fallacy: evaluating past decisions with the benefit of hindsight, assuming actors knew the outcome when they acted. Product-market fit commits the same error. It reinterprets early chaos as the inevitable prelude to success. It turns ambiguity into foreshadowing. It paints a coherent path through what was, at the time, a fog of half-baked ideas and desperate improvisation.

Marc Andreessen coined the term in 2007, describing the elusive moment when a startup finally gets traction. But even he admitted the definition is more about emotional intuition than measurable threshold: "You can always feel product-market fit when it’s happening. The customers are buying the product just as fast as you can make it... You’re hiring sales and customer support as fast as you can."

It reads more like a mood than a metric. Which is the problem.

Post-Hoc Clarity and Survivor’s Euphoria

The retrospective illusion of product-market fit comes from a cognitive glitch: we’re built to see stories. Especially around success. Most founders who “find” PMF didn’t predict it. They didn’t test their way into a perfect match between need and solution. They tried something, it sort of worked, they kept going, it worked a little more, they changed it, and eventually, something stuck. At that point, the narrative hardens.

This process looks a lot like stumbling. But hindsight pressure makes it look like navigation. Like you knew the destination the whole time.

In reality, many of the most iconic startups were started as entirely different products. YouTube was a dating site. Slack was a failed MMO. Twitter was a podcast platform. Shopify began as a snowboarding equipment store. PMF didn’t descend from the clouds. It got discovered by accident and then mythologized by pitch decks.

The Paper-Thin Threshold

People talk about PMF like it’s a binary switch: either you have it or you don’t. In practice, it's more like tectonic pressure that builds until something snaps. Or doesn’t. The difference between a “dead” startup and a breakout one often isn’t the product. It’s endurance. It’s liquidity. It’s who your friends are. Sometimes, it’s dumb luck.

I’ve met founders with almost identical products, similar features, same value prop. One raised a seed round and flamed out in 18 months. The other got a few angels on board, hit a slightly more desperate segment of the market, and now has $30 million in ARR. If you squint hard enough, the difference looks like product-market fit. If you’re honest, it looks like a random walk through a power-law distribution.

Brute Psychological Endurance

The startups that “make it” are often the ones that didn’t die. Which sounds tautological. But bear with me. Founders who last long enough eventually accumulate surface area: users, attention, capital, anecdotes. Every week they stay alive, they’re more likely to run into a new insight, a new distribution channel, a better niche. This isn’t strategy in the traditional sense. It’s evolutionary drift under resource constraints.

Psychologically, this kind of endurance looks like obsession. Or delusion. There’s a fine line between the two. Steve Blank likes to say that startups are a series of failed experiments until something catches. That framing is closer to the truth. Product-market fit isn’t the product’s doing. It’s the founder’s refusal to stop moving long enough for the product to be called a failure.

Network Spillover and the Myth of Isolation

We love the idea of the lone genius tinkering in isolation. But most of what we call PMF is a function of network effects—social, reputational, financial. If you’re well-networked in Silicon Valley, you can hack distribution before your product is good. If you’re followed by journalists and influencers, you can shortcut attention. If your investor is a power node, your B2B SaaS gets trials before the onboarding flow even works.

So when one founder gets traction and another doesn’t, it might look like a difference in product-market fit. But the playing field is tilted long before the user signs up.

In that sense, PMF is less about matching a product to a market and more about matching a founder to a moment. Sometimes the product is bad but the founder has cachet. Sometimes the market is sleepy but the team knows how to provoke it into interest. These nuances don’t fit into a neat three-letter acronym.

Startups are obsessed with charts. Growth curves. Retention graphs. Churn slopes. We look for inflection points because they feel like evidence. And when a line goes up sharply, we reach for language to explain why. “That’s when we hit product-market fit.”

But there’s a statistical hazard in this too. Many curves that look exponential are really logistic. They flatten. They overshoot. They regress to the mean. Some of the most stunning early-stage curves were fueled by media attention, ad arbitrage, or viral luck. And when they plateau, founders are left confused: “We had PMF. What happened?”

What happened is that the curve was never proof. It was a phase.

A Better Frame: Market-Momentum Fit

Instead of talking about product-market fit as a moment of truth, maybe we should talk about market-momentum fit: the period when the market is moving faster than your mistakes can kill you. When attention, timing, and demand converge just long enough to let you fix things in motion.

This frame is more honest about volatility. It recognizes that most early traction is fragile. That early success is often built on a shaky stack of temporary hacks. And that founders aren’t “wrong” if the curve stalls. They’re just still in the game.

Why This Matters

The PMF myth is damaging because it creates false hope, then false guilt. If you believe in product-market fit as a binary, then failing to find it feels like personal failure. Like your product was broken. Or your vision was off. Or your strategy flawed. But maybe your timing was off by a year. Maybe your competitor got the right tweet. Maybe your email hit the wrong inbox.

And when things do work, founders lean on the myth to justify irrational scale. “We found PMF, now we raise.” The myth becomes the license. And when growth stalls, they don’t know how to interpret it. Because the story said this stage was over.

The Fiction We Choose

Humans like stories with arcs. We like turning points. We like explanations. Product-market fit gives us all three. It lets investors pretend there’s a science to their bets. It lets founders pretend they’ve unlocked the code. It lets employees feel like they joined something real.

But reality is messier. Some companies hit early traction and flame out. Others grind for years and suddenly break through. The map is distorted. And there is no dotted X that says: "Here lies PMF."

There is only persistence, probability, and the unbearable ambiguity of trying to build something new in public.

So the next time someone tells you they found product-market fit, ask them what they changed the week before it happened. Ask them what their metrics looked like the month before. Ask them how many different markets they explored before they landed in this one. Then ask them if they think it will last.

If they’re honest, they’ll say they don’t know.

Because that’s the only answer that’s ever been true.