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How This Developer Built a $440K/Month Fitness App by Cloning a Competitor
TL;DR: Julian discovered Fitbod had great UX but dangerously bad workout logic. He built Fitbod's interface with proper workout engine in 2-3 months. Posted technical 'how I built it' on Reddit, got 300K impressions and thousands of users. Added subscription and got first paying customer in 10 minutes of launching ads. Translated to Spanish and ran ads in South America for <$50/day. Main distribution is paid ads spending ~1/3 of revenue. Uses Meta Ad Library to copy competitors' winning ad creative. Hard paywall BEFORE showing generated workout converts surprisingly well. Built with React Native/Expo, .NET backend, uses Cursor carefully.
Key Insights
- Identify competitor weaknesses through personal use - Fitbod had great UX but dangerous workout logic
- Reddit technical posts can generate thousands of users instantly
- Hard paywall BEFORE showing product value can work
- Target cheaper ad markets first (South America) before expensive US market
- Copy winning ads from competitors using Meta Ad Library
Actionable Takeaways
- Use competitors' products deeply to identify specific weaknesses
- Post technical 'how I built it' content on Reddit to attract developers
- Test paid ads immediately after adding monetization
- Translate app and target Spanish-speaking markets where ad costs are lower
- Browse Meta Ad Library to copy competitors' winning ad creative
Principles Validated (2)
Read full article on youtube.comAdded Feb 4, 2026