Singular or Plural App Store Keywords: What Apple Says and How to Test

Apple's keyword guidance says to maximize the number of words that fit in the limit by avoiding plurals of words you have already included in singular form (Apple: product page). That is the whole statement. Apple does not describe stemming, plural matching or how word forms are treated in ranking. Anyone who states exact behavior as a rule is describing observation, not documentation.

The keyword field holds 100 bytes (App Store Connect reference). Plural forms eat that space quickly. For the hypothetical habit tracker Streakly:

You save 23 bytes, which is room for three or four other words such as planner, checklist and journal.

Some plurals are not variants. "Glasses" is not "glass", "jeans" has no singular people type, and a plural can signal a different intent ("flashcard" the object versus "flashcards" the app type). For those, check the top 10 of both forms in the App Store. If the two lists differ in the kinds of apps shown, treat them as two phrases and decide each on its own merits, as you would in any keyword research.

Use this when a phrase is important enough to spend a slot on.

1. Pick the phrase and a control. Choose one singular/plural pair (for example reminder and reminders) and one unrelated keyword whose rank should not change.
2. Record the baseline. Note your rank for both forms in one country. LocalASO stores daily history, or write it down by hand.
3. Change one thing. Put only the singular in the keyword field and make sure neither form appears in your name or subtitle.
4. Wait. Apple says that after you update app information, it may take up to 24 hours for changes to appear (Apple: view and edit app information). Apple does not say how long ranking takes to settle, so check daily for a week and keep the control stable; see how long keyword changes take.
5. Compare. If your rank for the plural form holds near the singular, the store treated them alike for you in that country. If it drops, the plural carries its own value there.

One test is one data point for one storefront and one moment, so repeat it before you change a whole list. Keep other metadata unchanged during the test.

The control matters. If your rank for the unrelated control keyword also jumps, something else changed (a new version, new ratings, a seasonal shift), and the singular/plural result is not clean. Write down the date, the exact field text before and after, and the country, so the next test starts from facts. If the plural keeps its rank while the singular is the only form in your field, you have learned something real about your own listing: you can keep the singular and spend the saved bytes elsewhere.

Plural rules differ by language and many languages inflect more forms than English. Test per language and do not copy an English decision into other storefronts.

Add both forms to the board, check them in your target countries and compare rank, estimated volume and difficulty side by side. The numbers are estimates from rating counts, not Apple search counts. Use the keyword field checker to count bytes before you ship. For the general field rules, read what to put in the keyword field.