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. For those censored keywords Sonar computes a proprietary proxy estimate 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_proxy exposes the estimate alongside the Apple value.

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.

As a rough guide: 0–30 is low competition (a real opportunity), 30–60 is moderate, and 60–100 is highly competitive.

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.