How Popularity & Difficulty scores work

Popularity (0–100)

Popularity measures how much a keyword is searched in the store. A higher score means more people are typing that term, so ranking for it can drive more installs.

On iOS, Popularity is Apple's own number. Sonar reports Apple's Search Popularity — the 5–100 demand score Apple itself publishes for every keyword in its Search Ads console. It's a real Apple-reported value, not a model estimate. Most ASO tools reconstruct this number from indirect signals; Sonar sources it from Apple directly.

One caveat Apple bakes in: many niche terms are floored at 5, so a wide band of long-tail keywords all read "5" even though their real demand differs. Since October 22, 2026 Apple reports real values down to about 20, so only keywords below that read 5. For those Sonar shows its own proxy estimate, at most 18, so you can still tell them apart. The API is explicit about which value you're seeing: popularity_source says apple or proxy, and popularity_apple carries Apple's own reading alongside.

On Android, Google publishes no equivalent number, so Popularity is an estimate — but a calibrated one. We benchmarked it against real Apple Search Popularity for the same 57 keywords across both stores: mean absolute error of 12.5 points, Spearman rank correlation 0.775. Its primary signals are a Google Play autocomplete depth probe and the install volumes of the top-10 ranking apps.

Difficulty (0–100)

Difficulty estimates how hard it is to reach the top of the results for a keyword. A higher score means the apps already ranking are strong and well-established, so displacing them takes more work. We calculate it by analyzing the apps that currently rank for the term and weighing how formidable they are as a group.

What feeds the score

Without giving away the recipe, the factors that push Difficulty up include:

• Title relevance of the top apps — keywords sitting in app titles signal strong, direct competition.
• Strength of the incumbents — install volumes, review counts, and ratings of the apps already ranking.
• Market saturation — how many established apps are competing for the same term.
• Brand pull — branded terms are dominated by their owner and are hard to break into.

What the ranges mean

The bands below match the colors Sonar uses wherever a Difficulty score appears. A score describes the apps ranking today, so read it against your own app: a keyword that is out of reach for a brand-new app can be winnable for one with a few thousand ratings.

• 0–30, low. Few of the top apps target the term in their title, and the incumbents have modest review counts. A new app with a sharp title match can reach the top results. Most keywords this low are long-tail phrases.
• 31–60, moderate. A mix of small and established apps. Winnable when the strongest of the top few apps is close to your size, so check them before you commit.
• 61–80, hard. Established apps with large review counts hold most of the top 10. Realistic once your app is already one of the stronger apps in its category.
• 81–100, very hard. Category-defining terms and brand names, held by apps with millions of installs. Not a realistic target for most apps.

Difficulty by category

Sonar publishes difficulty pages for 87 category head terms. On the US App Store (refreshed September 2026), none of them scored 30 or below, and the median was 69. Health & Fitness had the highest category median (74), followed by Photo & Video (70); Finance had the lowest (59). The lower-scoring head terms in every category named a specific tool rather than a category: "kanban board" (33), "photo compress" (34), "unit converter" and "push-up counter" (36), "tip calculator" (37). Being specific lowers difficulty more than picking an easier category does.

App Store vs Google Play

The same keyword can score very differently on the two stores, and neither store is uniformly harder. For those 87 terms, Google Play scored lower on 55 and higher on 32. The median gap was 3 points, but 17 terms were 15 or more points apart: "tip calculator" scored 37 on the App Store and 17 on Google Play, "mortgage calculator" 54 and 17, while "file manager" went the other way, 65 and 87. The stores also rank differently: the App Store ranks on the title, subtitle and hidden keyword field, while Google Play indexes the full description and shows install ranges on every listing. Score each store separately rather than carrying an iOS keyword list over to Google Play.

The branded-keyword exception

A brand name is the one case where the score doesn't answer the question. People who search "spotify" or "canva" want that app, so ranking there brings almost no installs even when the results look beatable. Brand terms usually score high anyway, because the owner holds #1 with enormous install volume. Phrases like "alternative to …" can show moderate difficulty and reach people who are shopping around, but they are usually low-volume, and App Review Guideline 2.3.7 bars trademarked terms and other apps' names from your metadata. Treat brand names as off-limits whatever their score.

Gap = Popularity − Difficulty

The Gap column is simply Popularity minus Difficulty. A large positive Gap is the sweet spot — high demand with low competition. These are the keywords worth prioritizing first.

Opportunity (0–100)

Opportunity is Sonar's single "should I target this?" number: it starts from how easy the keyword is (100 − Difficulty) and weights that by real demand, with low-popularity keywords damped so a keyword nobody searches can't score well just because it's easy. Keywords your app already ranks #4–#30 for get a boost — relevance is proven there, and a small metadata push has the biggest payoff. It's the default sort in the Discovered tab: work from the top down.

Relevance (0–100)

Relevance is an AI-assessed score of how well the keyword's searcher intent matches your app, captured when the keyword is discovered. A keyword can have great Popularity and Difficulty numbers and still be useless if the people searching it want something else — Relevance is the guard against that, especially for keywords surfaced from competitors. Sort by it to push plausible-but-irrelevant terms out of view.

Why three ASO tools show three different numbers

If you compare Sonar, AppTweak, and Appfigures side by side, the Popularity and Difficulty values won't match — and that's expected. Every ASO tool builds these scores from its own data sources and its own proprietary model, then normalizes them onto its own scale. There is no single industry-standard number.

There is one exception: iOS Popularity. Sonar doesn't estimate that one — it reports the Apple Search Popularity value Apple itself publishes. So when tools disagree on an iOS keyword's popularity, the others are estimating the number Sonar reports.

For everything else, the right way to use any of them is to rank keywords against each other within one tool — not to compare absolute numbers across tools. Inside Sonar, a keyword at 70 popularity really is more searched than one at 40; that relative ordering is what you act on.

We also validate our numbers against independent ground truth and publish the results — see How we check our data.

How to use them together

Hunt for keywords with high Popularity and low Difficulty (a positive Gap) — enough people are searching to matter, and the competition is beatable. Sort by Gap, filter out anything above your Difficulty comfort level, and start with the terms where you can realistically crack the top results.