Essay · ~3,500 words

Casey's Guide to Finding Product/Market Fit

Casey Winters · Casey Accidental (Casey Winters) Free Advanced

Winters, who led growth at Pinterest and Grubhub, reframes PMF as the point where users stop leaving, and shows how to read it off cohort retention curves rather than satisfaction scores. It is the most rigorous treatment of measuring fit as a trend over time, exactly the framing in your short answer. Best once you have some usage data to analyze.

  • PMF is when they stop leaving, measured by retention flattening
  • Satisfaction surveys mislead, revealed retention behavior does not
  • Use cohort analysis to watch fit as a trend, not a snapshot
Open on caseyaccidental.com ↗

It answers 2 questions

  1. How do I know when something we shipped is actually working versus just launched?
  2. How do I know if I've found product-market fit?

Read with it

  1. This is the essay that forces the honest question underneath your idea: are you building a growth company or a good small... Paul Graham Essay · ~20 min read Startup = Growth Paul Graham
  2. Turns the vague feeling of product-market fit into a number you can move. Ask users how they would feel if they could no longer... First Round Review Article · ~20 min read How Superhuman Built an Engine to Find Product/Market Fit Rahul Vohra
  3. The free tool for running the how-would-you-feel-without-this survey that underpins the Superhuman method, giving you a... Sean Ellis and GoPractice Tool · Free tool Product/Market Fit Survey Sean Ellis
  4. The single best thing ever written on customer conversations. It teaches you to ask about the customer's life and past... momtestbook.com Book · ~130 pages The Mom Test Rob Fitzpatrick
  5. The essay that put 'product-market fit' into the startup vocabulary. Read it for the gut-level description of what PMF feels... pmarchive.com Essay · ~15 min read The Only Thing That Matters Marc Andreessen
  6. The nuanced counterweight: PMF isn't a single binary moment, it can be lost, and 'market' is doing more work than founders... a16z.com Article · ~20 min read 12 Things About Product-Market Fit Andreessen Horowitz (a16z)
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