Eve knew they had product-market fit when customers found a bug that let them bypass invite restrictions. Users onboarded their entire firms months ahead of schedule, demonstrating an urgent, unmet need for the product.

Product-market fit isn't a sudden switch but a palpable shift in momentum. As a founder, you feel the change from pushing against the current (hard selling with little traction) to suddenly being pulled by it (easier sales, inbound interest). This directional change in velocity is the clearest signal that you're onto something.

This visceral analogy reframes product-market fit as an uncontrollable, overwhelming demand from the market. It's not just positive metrics; it's a state of being swarmed by customers. If you don't feel this intense 'market pull,' you haven't truly achieved it and must keep iterating.

Product-market fit isn't just growth; it's an extreme market pull where customers buy your product despite its imperfections. The ultimate signal is when deals close quickly and repeatedly, with users happily ignoring missing features because the core value proposition is so urgent and compelling.

Initially, customers often "round down," focusing on missing features. A key sign of product-market fit is when they start "rounding up"—their faces light up in demos, and they imagine the product's future potential, forgiving current limitations because they believe in the core value.

The ultimate test of PMF isn't surveys or usage metrics, but how indispensable your product is. If customers don't immediately notice and complain when it's gone, you haven't achieved true dependency. It's a visceral, high-signal test for any founder.

Investors warn that when potential customers delay adoption because your product isn't a top priority, it's a major red flag. This feedback almost always means 'never' and signals a fundamental lack of product-market fit, suggesting you are solving a 'nice-to-have' problem, not a 'must-have' one.

After experiencing numerous lukewarm responses to failed ideas, the intense, urgent demand from a customer for a successful product becomes an undeniable signal. The contrast between a polite 'maybe later' and a frantic 'how do I get this now?' makes true product-market fit impossible to miss.

Founders often over-index on early user complaints. However, if a product addresses a powerful, unmet demand, users will endure significant flaws. The existence of strong market "pull" is a more important signal than initial product imperfections. The market will effectively fund the product's improvement.