Every ASO tool shows you a keyword difficulty score, and most developers misread it. They sort by lowest difficulty, paste those words into their keyword field, and wonder why nothing happens. Or they chase a high-popularity term, get buried on page four, and conclude ASO does not work.

Keyword difficulty is one of the two numbers that should drive every keyword decision you make. Here is what it actually measures and how to use it as an indie iOS developer.

What Keyword Difficulty Measures

Keyword difficulty is an estimate of how hard it is to rank in the top results for a given search term. It is derived from the strength of the apps already ranking for that keyword: their download velocity, ratings volume, age, and how directly the term appears in their metadata.

A high difficulty score means the top results are established apps with strong signals, and a new app will struggle to break in. A low difficulty score means the competition is weaker and a well-optimized newcomer has a realistic shot.

The key word is estimate. Difficulty is a model, not a guarantee. Two tools can score the same keyword differently because they weight competitor signals differently. Use difficulty to rank your options against each other, not as an absolute truth.

Difficulty Is Only Half the Picture

Difficulty never travels alone. The other number is popularity (sometimes called search volume or a search score), which estimates how many people actually search the term.

Every keyword sits somewhere on this grid:

  • High popularity, high difficulty — head terms like “fitness” or “budget.” Lots of searches, but you will not rank as a small app. Skip these early.
  • High popularity, low difficulty — the rare sweet spot. Grab these immediately; they almost never last.
  • Low popularity, low difficulty — long-tail terms. Each sends a trickle of traffic, but you can actually rank, and they add up. This is where indie apps win.
  • Low popularity, high difficulty — ignore. No upside.

A low difficulty score is worthless if nobody searches the term. A high popularity score is worthless if you cannot rank. You are always looking for the best ratio of popularity you can realistically capture to difficulty you can realistically beat.

How Difficulty Changes With Your App’s Strength

Difficulty is relative to you, not absolute. A keyword that is “hard” for a brand-new app with 12 ratings is “easy” for the same app a year later with 4,000 ratings and steady downloads.

This is why the right keyword set is a moving target. Early on, you target lower-difficulty long-tail terms because those are the only ones you can win. As your app accumulates ratings and download velocity, your ability to rank for harder terms grows, and you promote tougher keywords into your title and subtitle. We cover that progression in the keyword promotion ladder and improving your ranking with a keyword ladder.

How to Use Difficulty Scores in Practice

  1. Build a candidate list first. Use AI suggestions, competitor keyword gaps, and autocomplete to gather every relevant term. Do not filter yet.
  2. Plot popularity against difficulty. Most tools let you sort or visualize both. You are hunting for terms with usable popularity and difficulty at or below what your app can currently beat.
  3. Match difficulty to your placement. Your title and subtitle carry the most ranking weight, so reserve them for the highest-value terms you have a real shot at. The keyword field is where you stack lower-difficulty long-tail terms. See the keyword field as an underused lever.
  4. Never repeat across fields. Difficulty does not stack by repetition. Repeating a word in your title, subtitle, and keyword field wastes characters. See keyword and subtitle duplication.
  5. Re-check difficulty after you gain strength. Re-run your difficulty estimates every optimization cycle. Terms that were too hard three months ago may now be in reach.

The Mistake to Avoid

Do not sort by lowest difficulty and stop there. The lowest-difficulty keywords are often low-difficulty because almost nobody searches them. You will rank number one for a term that sends two installs a month.

The job is not to find easy keywords. It is to find the hardest keywords you can still realistically rank for, because those are the ones with enough search demand to matter. Difficulty tells you what is in reach; popularity tells you whether reaching it is worth the effort.

Try Marteso Free

Marteso shows popularity and difficulty side by side for every keyword, suggests terms with AI, and lets you push your chosen keywords straight into your App Store Connect metadata without leaving the tool.

The free tier gives you one app, 50 tracked keywords, and daily rank updates with no credit card required. Start at app.marteso.com.