Validation guides
Product Validation: Problem, Prototype, Willingness to Pay
Product validation is often treated as one test. It is three, in order: is the problem real, does your prototype solve it, and will people pay. Skipping ahead is how founders end up with a product people like and do not buy.
Product validation tests three things in sequence: that a specific group has the problem, that your prototype solves it in a way they notice, and that they will pay a price that works for you. Each stage needs its own evidence, and a pass at one stage says nothing about the next.
Founders preparing an MVP usually have the first stage half-done and the third not started. This guide covers all three and what counts as a pass at each.
Key takeaways
- Three stages, in order: problem, prototype, willingness to pay.
- The problem stage needs interviews, about recent, specific experiences.
- The prototype stage needs observed use, not opinions about screenshots.
- The price stage needs a real ask, such as a pre-order, a deposit or a paid pilot.
- After launch, measure how disappointed users would be without it. Superhuman's benchmark was 40% saying very disappointed.
What are the stages of product validation?
Problem validation, solution validation and willingness-to-pay validation. Each answers a different question and needs different evidence.
| Stage | Question | Evidence that counts | Evidence that does not |
|---|---|---|---|
| Problem | Does this group have the problem, and does it cost them? | Interviews about the last time it happened | "Yes, that sounds like a problem" |
| Prototype | Does our solution solve it in a way they notice? | Watching them complete the task with it | Likes on a screenshot |
| Willingness to pay | Will they pay a price that works? | A pre-order, deposit, signed pilot or payment | "I would pay for that" |
Our business idea validation checklist covers the first stage in detail. This guide focuses on the second and third.
How do you validate a prototype?
Put it in front of people who have the problem, give them the real task, and watch. Count whether they finish it, where they get stuck and whether they ask to keep using it.
A prototype can be much less than a product: clickable screens, a spreadsheet with formulas, or a service you run by hand behind a simple interface. What matters is that the person uses it on their own task, not a demo you narrate.
Three things to record in every session:
- Completion. Did they get the outcome they came for?
- Friction. Where did they hesitate, ask for help or give up?
- Pull. Did they ask when they could use it again, or offer their own data to try it?
The third is the strongest signal at this stage. Politeness produces compliments; real need produces requests.
How do you test willingness to pay before launch?
Ask for money, or a commitment that stands in for it, at a stated price. Measure how many accept, and listen carefully to why the others decline.
Buffer tested pricing before it had a product. Joel Gascoigne added a pricing page between the landing page and the sign-up, and explained: "The extra step tests the pricing (by detecting which plan they click on) and also tests further the demand for the product" (Buffer).
Stronger tests, in order:
- A priced offer page. Measures clicks on a price.
- A pre-order or deposit. Measures a small payment.
- A paid pilot. Measures a real budget decision, often with a signature.
The Mom Test, as summarised by Sachin Rekhi, lists financial commitments such as "letters of intent, pre-orders, deposits" as the clearest form of validation. The same summary quotes Fitzpatrick: "it's not a real sales lead until you've given them such a concrete chance to reject you."
How do you know the product is validated after launch?
Ask active users how they would feel if they could no longer use the product. If at least 40% say very disappointed, you have a strong signal. Below that, find out who the enthusiastic users are and build for them.
This is the survey Superhuman used, based on work by Sean Ellis. The question is "How would you feel if you could no longer use Superhuman?", with three answers: very disappointed, somewhat disappointed, not disappointed. Ellis found that companies where more than 40% of users answered "very disappointed" tended to grow well. Superhuman first scored 22% in summer 2017, then nearly doubled the score to 58% within three quarters by focusing on the users who loved it most (First Round Review).
That score belongs to after launch. Before launch, the stages above are the evidence you have. Our guide to product-market fit covers what comes next.
What are the most common product validation mistakes?
Testing the prototype before confirming the problem, testing with people who are not buyers, and treating interest as a proxy for payment.
- Starting at the prototype. A good prototype for a problem nobody has still fails.
- The wrong testers. Other founders and friends are easy to recruit and rarely the buyer.
- Interest as payment. Sign-ups and compliments do not predict purchases.
- Changing everything at once. If you change the buyer, the prototype and the price together, you cannot tell which change mattered.
- No stopping rule. Decide before each stage what result would send you back a stage.
Where does NELL fit in product validation?
Before the first stage. NELL's reports test whether the problem, market and pricing hold up on desk research, so your interviews and prototype tests start from the weakest assumption.
Quick Validate is free and gives a score, a verdict and next moves. DeepValidate adds live research with sources, including a "Can we monetize?" pillar that looks at pricing, unit economics and the revenue model. See a full example in the sample report.
Frequently asked questions
What is the difference between product validation and idea validation?
Idea validation tests whether the problem and market are real. Product validation goes further and tests whether your specific solution solves the problem and whether people will pay for it.
Can you validate a product without building it?
Partly. You can validate the problem and willingness to pay without a product, using interviews, priced offer pages and pre-orders. Validating the solution needs at least a prototype people can use.
How many users do you need to validate a prototype?
There is no fixed number. Watch people use it until the same friction points and the same reactions keep repeating, and make sure they are people who fit your buyer.
What is the 40% rule for product-market fit?
It comes from Sean Ellis: if at least 40% of active users say they would be very disappointed if they could no longer use a product, it tends to have strong product-market fit.
Is a pre-order enough to validate a product?
It is strong evidence of demand at that price. It does not yet prove the product solves the problem well, which you learn once people use it and either stay or leave.
Start where you are
Find the weakest assumption before you test the prototype.
Sources
- First Round Review, How Superhuman Built an Engine to Find Product/Market Fit (2018)
- Buffer, Idea to Paying Customers in 7 Weeks: How We Did It (2011)
- Sachin Rekhi, A Primer on Talking to Customers From The Mom Test
The 40% benchmark is a widely used heuristic, not a guarantee. Validation evidence reduces risk; it does not remove it.