What Is Customer Development?
Customer development is the process of rigorously testing your business assumptions with real customers before building. Learn how to run customer discovery properly.
Key Takeaways
- Customer development tests your assumptions about the problem, the customer, and the solution before you build
- The goal of early interviews is to learn, not to sell — leading questions give misleading results
- The Mom Test: ask about behaviour and past actions, not opinions and hypotheticals
- Talk to at least 20-30 potential customers before drawing conclusions
What customer development is
Customer development is a rigorous, systematic process of testing the fundamental assumptions of a business — about the problem, the target customer, the proposed solution, and the business model — with real potential customers before investing heavily in building the product. Developed by Steve Blank and popularised by Eric Ries in The Lean Startup, it is the antidote to the common founder mistake of building in isolation and then discovering that nobody wants what you built.
The four stages
Steve Blank defined four stages of customer development. Customer Discovery: test whether your hypotheses about the problem and customer are correct. Customer Validation: test whether your solution to the validated problem has a repeatable, scalable sales process. Customer Creation: build end-user demand and drive it into your sales channel. Company Building: transition from a learning organisation to an execution organisation. Most startups skip directly to Company Building without ever properly completing Discovery and Validation.
How to run a discovery interview
Customer discovery interviews are structured conversations designed to test your assumptions about the problem. The questions should focus on behaviour and past experience, not opinions and hypotheticals. Tell me about the last time you faced [problem]. How did you deal with it? What tools or processes do you use? What is most frustrating about your current approach? How much time or money does this problem cost you? These questions reveal whether the problem is real and how the person currently addresses it.
The Mom Test
Rob Fitzpatrick's The Mom Test is required reading for any founder doing customer discovery. The core insight is that if you ask your mum whether your business idea is good, she will say yes because she loves you. The same dynamic applies with any customer who wants to be polite. To avoid misleading feedback, ask about facts and behaviours rather than opinions and hypotheticals. Do not ask: would you use a product that does X? Instead ask: how do you currently handle X? What did you do last time you needed X? How much did that cost you? Past behaviour predicts future behaviour. Opinions do not.
How many interviews are enough
A common question is how many customer interviews are needed before drawing conclusions. The practical answer is around 20-30 for each distinct customer segment. After around 5-8 interviews with a consistent customer type, patterns will begin to emerge — the same problems, the same language, the same workarounds appearing repeatedly. By 20-30 interviews, you will have either validated your hypothesis strongly enough to proceed or gathered sufficient evidence to challenge it. The interviews should stop when you are no longer learning new things — when you can predict what the next person will say before they say it.