Product-Market Fit

Product-market fit (PMF) is the degree to which a product satisfies the needs of a specific market. Marc Andreessen described it as "being in a good market with a product that can satisfy that market." When you have it, customers are signing up faster than you can handle, retention is strong, and word-of-mouth is driving growth. When you do not have it, everything feels like pushing a boulder uphill.

There is no single metric that proves product-market fit, but several indicators strongly correlate with it: retention curves that flatten (users keep coming back), organic/referral growth exceeding 40% of new signups, NPS above 40, and the Sean Ellis test (more than 40% of surveyed users say they would be "very disappointed" if the product disappeared).

Achieving PMF is the single most important milestone for an early-stage startup. Before PMF, spending heavily on marketing, sales, or infrastructure is premature: you would be scaling something that does not yet work. After PMF, the challenge shifts from building the right thing to scaling it efficiently. Most successful startups pivot one or more times before finding PMF, which is why runway management and iteration speed are so critical in the early stages.