The 6 Signals Behind Keyword Popularity Scores

Most ASO tools give you a keyword popularity number between 1 and 100 and call it a day. You're supposed to trust the number, pick keywords with high scores, and hope for the best. But if you don't understand what drives that number, you can't make smart decisions about edge cases -- and in ASO, edge cases are where indie developers find their best opportunities.

At ASO Toolkit, we compute keyword popularity from publicly available iTunes Search API data using a 6-signal model. This article explains exactly how each signal works, what it contributes to the final score, and how you can use that knowledge to pick better keywords.

How the scoring works

When you add a keyword, we search the iTunes Search API for that term and analyze the results. The apps that come back tell us a lot about the keyword: how many apps target it, how strong the competition is, and whether the keyword represents genuine user search intent or just noise.

Each signal contributes points to a raw score, which is then clamped to a 5-100 range. Here's what goes into it.

Signal 1: Result count (0-25 points)

What it measures: How many apps appear in search results for this keyword.

How it works: More results generally means more developers are targeting this keyword, which is a proxy for search volume. If many developers think a keyword is worth optimizing for, there's probably real user demand behind it. The score scales linearly: each result contributes 2.5 points, up to a maximum of 25 points at 10 results.

What to watch for: A high result count confirms the keyword has a real market. But result count alone doesn't tell you if you can compete there. That's what the other signals are for.

Signal 2: Leader strength (0-25 points)

What it measures: How dominant the top-ranking app is, based on its review count.

How it works: We take the maximum review count among all results and apply a logarithmic scale. An app with 1,000,000 reviews scores near the maximum; an app with 100 reviews scores much lower. The log scale matters because the difference between 10 and 1,000 reviews is more meaningful than the difference between 500,000 and 1,000,000.

Why it matters: A keyword where the top result has millions of reviews (think "weather" or "calculator") is popular but probably not where you want to compete. A keyword where the leader has 5,000 reviews? That's interesting. The popularity is there, but the throne isn't untouchable.

Practical tip: Look for keywords where leader strength is moderate (8-15 points). That signals genuine popularity without an entrenched monopoly at the top.

Signal 3: Title match density (0-15 points)

What it measures: What percentage of competing apps include the keyword in their app title.

How it works: We check how many of the search results contain your keyword (case-insensitive) in their track name. If 50% of results have the keyword in their title, that's a strong signal that developers consider this keyword important enough to spend precious title characters on. The contribution caps at 15 points.

Why it matters: Title match density is one of the clearest signals of keyword intent. When developers put a keyword in their title -- sacrificing other words in that 30-character limit -- they believe users are actively searching for it. High title match density combined with a reasonable result count is a strong indicator of a valuable keyword.

Practical tip: If a keyword has decent result count but very low title match density, it might mean the results are tangentially related rather than directly targeting that term. The keyword might not be as valuable as the result count suggests.

Signal 4: Market depth (0-15 points)

What it measures: How many competing apps have substantial user bases (over 1,000 reviews).

How it works: We count the apps in the search results with more than 1,000 reviews and compute that as a ratio of total results. A market where multiple established apps compete indicates sustained, ongoing user interest -- not just a temporary trend.

Why it matters: Market depth separates keywords with lasting value from flash-in-the-pan terms. A keyword might have 10 results, but if only one app has more than 1,000 reviews and the rest have 12, the "market" is shallow. Compare that to a keyword where 6 out of 10 results have thousands of reviews -- that's a deep market with real, ongoing search volume.

Practical tip: For long-term ASO strategy, prioritize keywords with moderate-to-high market depth. Shallow markets can disappear or shift quickly. Deep markets reward consistent optimization.

Signal 5: Specificity penalty (0 to -10 points)

What it measures: Whether a keyword is too generic to be useful.

How it works: Single-word keywords that return many results get penalized. Very short single words (3 characters or fewer) receive a harsher -10 point penalty. The logic: a search for "run" returns everything from running trackers to business management tools. The results are noisy, and a high result count for a generic term doesn't actually indicate that users searching for your type of app will find you.

There's an exception: well-known uppercase acronyms (AI, VPN, GPS, PDF) are exempt from this penalty. These short terms carry specific meaning despite their brevity.

Why it matters: This is the signal that prevents you from chasing vanity keywords. "Photo" might return tons of results with strong leaders, giving it high scores on the other signals. But it's so generic that ranking for it is nearly meaningless -- users searching for "photo" could want a camera app, an editor, a gallery, a stock photo service, or a social network.

Practical tip: Prefer multi-word keywords whenever possible. "Expense tracker" is almost always better than "expense" alone. Two-word and three-word phrases capture clearer user intent and face more focused competition.

Signal 6: Exact phrase bonus (0-10 points)

What it measures: Whether competing apps use the exact multi-word phrase in their title.

How it works: For keywords with two or more words, we check how many competitors include the entire phrase (as a complete word boundary match) in their app title. If developers are using the exact phrase "habit tracker" in their titles, it confirms that users search for that specific combination of words. This bonus only applies to multi-word keywords.

Why it matters: This signal rewards specificity. It's the counterpart to the specificity penalty -- while generic single words get penalized, precise multi-word phrases that developers actively use get a boost. It helps distinguish between a keyword like "daily planner" (which apps explicitly target) and a two-word combination that just happens to appear in results by coincidence.

Practical tip: When brainstorming keywords, test common two-word and three-word phrases that describe your app's core function. If the exact phrase bonus is high, you've found a keyword with clear, validated search intent.

Putting it all together

The six signals combine into a single popularity score between 5 and 100. But the real value isn't in the final number -- it's in the signal breakdown. Here's how to read it:

• High result count + high leader strength + low title match: Popular category, but the keyword itself isn't the primary way apps position themselves. Could be a secondary opportunity.
• Moderate result count + high title match + high exact phrase bonus: A focused keyword with clear intent. Often the best targets for indie developers.
• High everything + specificity penalty: You're looking at a generic term. Drill down into more specific variations.
• Low result count + low leader strength: Either an undiscovered gem or a keyword nobody searches for. Cross-reference with your own intuition about what users might type.

The keyword sweet spot for indie apps

Based on the signal model, the ideal keyword for an indie developer looks like this:

• Popularity score: 30-60. Enough search volume to matter, not so much that you're competing with giants.
• Result count signal: 10-18 points. Several apps targeting the keyword, confirming demand.
• Leader strength: 8-15 points. The top app is established but not untouchable.
• Title match density: 5+ points. Developers consider the keyword worth their title space.
• No specificity penalty. You're targeting a multi-word or meaningfully specific term.
• Some exact phrase bonus. The phrase has validated search intent.

You can see all six signal values for every keyword you track in ASO Toolkit. Use them to make decisions based on data, not guesswork. And when two keywords have similar overall scores, dig into the signals to understand which one actually represents a better opportunity for your app.