Keyword difficulty (KD) is a composite of the strength of the top-ranking apps for a query: their cumulative downloads, rating count, age in market, and the share of total clicks the top 3 results capture. A high-KD keyword has top results that are big, well-reviewed, long-established apps. A low-KD keyword has top results with weaker metadata, fewer reviews, or lower download velocity — and a well-optimized new entrant has a realistic chance of breaking in.
Different tools score KD on different scales. MWM uses a 0-10 scale where 10 is the absolute ceiling (terms like "instagram" or "tiktok" in the US). Apple and Google never disclose their own ranking signals, so every difficulty score is a third-party estimate built from observable downstream metrics. Absolute scores don't always line up across tools, but relative rankings of one keyword vs another usually do.
Across the MWM keyword tracker (91 countries), the median US App Store keyword sits at KD 8.13 on the 0-10 scale. Only 10% of US keywords are easier than KD 6.64. The hardest 1% (KD 9.44+) are the household-name brand terms. The distribution is heavily left-skewed: roughly 4 in 10 US keywords fall into the 8-9 bucket.
KD also scales the prize. In MWM's data, every 1 point of KD multiplies the daily download volume top-10 apps capture by roughly 3×: KD 4-5 keywords have top-10 apps averaging ~30 daily downloads, KD 7-8 averages ~380, KD 8-9 averages ~1,900, and KD 9-10 averages ~8,700 daily downloads. The flip side: easy keywords are winner-take-all (top 3 capture 95% at KD 2-3) while hard keywords spread the wealth (top 3 capture only 30% at KD 9-10).
Counter-intuitively, long-tail isn't easier in ASO. 1-word US keywords have median KD 8.04. 6-word keywords have median KD 8.45 — slightly harder, not easier. The reason: any multi-word ASO keyword that survives the search-volume threshold is one users actually type, which means competitors target it too. The pure long-tail free lunch that exists on Google web doesn't exist on the App Store.
What different KD scores actually mean
| KD bucket | Top-10 median daily downloads | Top-3 share of downloads | Realistic strategy |
|---|---|---|---|
| 3-4 | 30 | 79.2% | Winner-take-all niche — be #1 or skip |
| 4-5 | 29 | 73.1% | Indie new-entrant range — possible at low effort |
| 5-6 | 34 | 59.8% | Indie new-entrant range — possible at low effort |
| 6-7 | 80 | 46.1% | Sweet spot for serious ASO work |
| 7-8 | 380 | 42.4% | Established-app territory |
| 8-9 | 1,875 | 38.6% | Category leaders compete here |
| 9-10 | 8,708 | 30.1% | Brand-name terms only |
How to use KD: filter your keyword list by a difficulty ceiling that matches your app's weight class. A brand-new indie app should stay under KD 6 in the US, or move to an emerging market (Romania, Ghana, Algeria — median KD 6.26-6.34) where the ceiling is naturally lower. An established mid-tier app works in KD 6-8. Category leaders can target KD 8+, but only if their download velocity and rating profile can match the incumbents.