You can guess whether an app idea will work — or you can look at the numbers first.

These three sites won't build the product for you. But they'll save you months of building something nobody pays for.

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1. TrustMRR — see what indie products actually earn

TrustMRR is a leaderboard of verified startup revenue. Founders connect Stripe, LemonSqueezy, or similar payment tools, and the platform pulls real MRR directly from the source. No screenshots, no self-reported numbers.

Browse by category, check who's growing, see what's for sale. When you're asking "does this idea make money?" — you're answering with data, not vibes.

Use it when: you're validating a SaaS or indie product idea and want proof that similar apps are earning.

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2. Sensor Tower — open the App Store black box

Sensor Tower shows what's happening inside the app stores. Download estimates, revenue forecasts, category rankings, ad spend — for your competitors and the apps you want to beat.

Pick a niche, filter by country, see which apps are climbing. If a category looks crowded but nobody's making money, you'll spot that here before you write a line of code.

Use it when: you're building a mobile app and need the big picture — market size, top players, growth trends.

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3. Appkittie — understand why apps win, not just what they earn

Appkittie goes one level deeper. You find a niche, then see which apps dominate it — their downloads, revenue estimates, ad creatives, influencer collabs, and ASO keywords.

TrustMRR tells you what earns. Sensor Tower shows how big the market is. Appkittie helps you figure out why certain apps get downloaded and others don't.

Use it when: you've found a promising niche and want to reverse-engineer the winners before you ship.

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Quick comparison

Don't build blind. Spend an hour on these three before you commit to the next idea.