Runway's founder knew he had found product-market fit not just from revenue, but when a major customer, AngelList, began running its business on the platform and became an evangelist. Deep adoption by a respected company is a far stronger signal of PMF than early sales traction alone.

Metrics can be misleading. The founder's true "aha" moment for product-market fit came from solving a complex, real-world problem posed by a skeptical expert during a live demo. When the product solved in seconds what took the customer's team two weeks, it provided undeniable proof of value in a high-stakes environment.

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.

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.

For Ethic, the feeling of true product-market fit wasn't just hitting metrics, but the moment they helped an advisor win a major new client. The founder realized this success was a replicable playbook that could be repeated, creating a flywheel for growth. The metrics then followed this initial breakthrough.

You've achieved product-market fit when the market pulls you forward, characterized by growth driven entirely by organic referrals. If your customers are so passionate that they do the selling for you, you've moved beyond just a good idea.

Sales are a vanity metric for product-market fit. The real test is having ~25 customers who have successfully implemented your product and achieved the specific ROI promised during the sales process. If you don't have this, you have a product problem, not a go-to-market problem.

The ultimate validation of product-market fit isn't retention or satisfaction scores, but the percentage of new revenue driven by customer referrals. When 30% or more of your new top-line monthly revenue comes from existing customers recommending your product, you've built something people genuinely love and need.

Founders without product-market fit constantly optimize small things, believing better execution is the key. In contrast, with PMF, solid execution yields disproportionate results. Sales calls close without "Jedi mind tricks" because customers want the product.