Stop building products nobody wants. Spend 100 Euro and one week to know if your idea works.
By David Friedman, Founder of AppBrewers
I have built 80+ web apps. The ones that failed had one thing in common: nobody validated the idea before building. The ones that succeeded all used the same 100 Euro test. Here it is.
The 100 Euro Validation Test
Day 1-2: Build a Landing Page
Create a one-page website that explains your idea. Include:
- A clear headline (what problem you solve)
- 3 bullet points (how you solve it)
- A waitlist form (email only)
- A price (yes, put a price on it)
Tools: Carrd (free) or Typedream (0-19 Euro).
Time: 2-4 hours.
Day 3-5: Run Ads
Spend 50 Euro on Meta or Google ads. Target your ideal customer.
| Platform | Best For | Cost Per Click |
|---|---|---|
| Meta (Facebook/Instagram) | B2C, local services | 0.50-2 Euro |
| Google Search | B2B, high intent | 1-5 Euro |
| TikTok | Young demographics | 0.30-1 Euro |
Goal: Get 50-100 visitors to your landing page.
Day 6-7: Measure and Decide
| Metric | Target | What It Means |
|---|---|---|
| Landing page visitors | 50-100 | You have traffic |
| Waitlist signups | 10+ (20%+) | People are interested |
| Email open rate | 40%+ | Your message resonates |
| Pre-orders | 3+ | People will pay |
Kill the idea if:
- Fewer than 10 people sign up
- Fewer than 3 people pre-order
- Your cost per signup is over 5 Euro
Proceed if:
- 10+ signups
- 3+ pre-orders
- Cost per signup under 5 Euro
Real Example: Conversify
When we validated Conversify (AI receptionist for small businesses):
| Metric | Result |
|---|---|
| Ad spend | 50 Euro |
| Landing page visitors | 87 |
| Waitlist signups | 22 (25%) |
| Pre-orders | 5 |
| Cost per signup | 2.27 Euro |
Decision: Proceed. We built the MVP in 4 weeks. First paying customer in week 5.
Common Validation Mistakes
Asking Friends and Family
Your mom will say your idea is great. She is not your customer.
Fix: Only count signups from strangers who found you through ads.
Building a Prototype First
A prototype takes weeks. A landing page takes hours. If nobody signs up for a landing page, they will not use your app.
Fix: Landing page first. Code second.
No Price on the Landing Page
If you do not put a price, you learn nothing about willingness to pay.
Fix: Always include pricing. Even if you change it later.
Giving Up After 50 Euro
50 Euro might not be enough to reach your audience. If you get 5 signups but they are highly engaged, that is enough.
Fix: Look at engagement, not just numbers.
Next Steps After Validation
| Stage | Action | Timeline |
|---|---|---|
| Validated | Build MVP | 4-6 weeks |
| 10 paying customers | Add features | 2-4 weeks |
| 100 paying customers | Scale marketing | Ongoing |
| 1,000 paying customers | Raise funding or hire | 6-12 months |
Read our full MVP guide: How to Build a SaaS MVP in 2026
Need Help?
We have validated 80+ ideas. If you want a second opinion on your concept:
Originally published on the AppBrewers Blog.
Top comments (0)