How to set the App Store keyword field: the 100-character rules

What the keywords field is

The keywords field is search text you enter in App Store Connect, per app and per localization. Apple’s search documentation says results are based on text relevance — matches for your app’s title, subtitle, keywords, and primary category — as well as user behavior such as downloads, ratings, and reviews. Keywords are one input to that text relevance.

The same page states that promotional text doesn’t affect search ranking, so it shouldn’t be used to display keywords. The keywords field itself isn’t shown on the product page and isn’t available from public data — ASO Lens can only read its contents for apps connected to App Store Connect.

Length and format: 100 characters, comma-separated, no spaces

Apple’s search documentation says keywords are limited to 100 characters total, with terms separated by commas and no spaces. Spaces are fine for separating words within a phrase; Apple’s example is Property,House,Real Estate (where Real Estate is one phrase).

Some things aren’t written down. For example, the pages checked don’t say whether a full-width comma or the Japanese reading mark (、) is treated as a separator. ASO Lens splits on both commas and 、 when it analyzes a field, but that is ASO Lens’s own implementation, not an Apple rule. If in doubt, use plain commas as Apple’s documentation describes.

“100 characters” vs. “100 bytes”: Apple’s pages don’t agree

Apple words the limit differently in two places. The search documentation says 100 characters; the App Store Connect Help property reference for Keywords says 100 bytes. In UTF-8, Japanese characters take three bytes each, so for Japanese keywords the two readings differ a lot. These two documents alone don’t settle which one the input field actually enforces.

ASO Lens works on the premise that App Store Connect’s counter and limit are character (code-point) based, and judges against 100 characters. It also computes the UTF-8 byte length and keeps it for reference, but doesn’t use it for scoring (src/core/scoring/rules/keywordsField.ts, docs/scoring.md). If the limit matters for your field, check the counter shown in App Store Connect’s input box.

The App Store Connect Help page also says each keyword should be “greater than two characters”. It doesn’t explain how that applies to Japanese terms or to phrases containing spaces.

Why not repeat words from the app name or subtitle

Apple’s search documentation says not to repeat words included in your app name, subtitle, or category. App Store Connect Help similarly says the app is already searchable by app name and company name, so you shouldn’t duplicate those in the keyword list. To get the most out of the 100-character limit, Apple lists what to avoid: plurals of words you’ve already included (Apple’s example is “climbs” and “climb”, which it says are considered duplicates), generic terms like “app” or “game”, filler words like “the” and “to”, and special characters such as # or @ unless they’re part of your brand identity.

Take care with the “why”. Apple tells you not to repeat words, but it doesn’t publish how its search algorithm treats a repeated word internally. What is firmly supported is: (1) the name, subtitle, and keywords are all inputs to text relevance; (2) repeating a word uses up a limited budget; and (3) Apple itself advises against it.

On the ASO Lens side, the keyword-coverage logic (src/core/keywords/coverage.ts) builds a dictionary from the title, subtitle, and keywords field, and when matches are the same length it prefers title, then subtitle, then keywords. So a term already covered by the title earns no extra coverage from also being in the keywords field, in ASO Lens’s model. The same question for the subtitle is covered in the subtitle guide; for title length rules, see the title guide.

What not to include: the review angle

Apple’s search documentation says improper use of keywords is a common reason for App Store rejections, and lists what not to include: unauthorized use of trademarked terms, celebrity names, or other protected words; terms not relevant to the app; competing app names; and inappropriate, offensive, or objectionable terms. App Store Connect Help likewise says names of other apps or companies aren’t allowed.

App Review Guideline 2.3.7 also asks you to assign keywords that accurately describe your app and not to pack metadata with trademarked terms, popular app names, pricing information, or other irrelevant phrases. It adds that Apple may modify inappropriate keywords at any time.

How localization applies

According to App Store Connect Help, metadata is held per localization and the one matching the user’s language setting is displayed. It also says users can search with localized keywords in all countries or regions where the App Store supports that language.

When you add a language, screenshots and most properties default to the primary language’s — except the description and keywords, which do not carry over. A newly added language needs its own keywords entered.

What the pages checked do not say: whether one language’s keywords are used for searches in another language, and how the “duplicate” idea applies to Japanese terms (Apple’s plural example is English). This article doesn’t invent a rule for either. ASO Lens’s own plural detection is likewise limited to English singular/plural pairs (+s / +es / consonant+y → ies) and isn’t applied to Japanese and other scripts (src/core/text/plurals.ts).

How ASO Lens evaluates the keywords field

ASO Lens looks at keywords in two ways.

• Keyword coverage. For each tracked keyword, it shows which parts are matched by the title, the subtitle, or the keywords field (src/core/keywords/coverage.ts). Keywords-field entries are split on commas or 、, and only terms of at least 3 characters (Latin) or 2 characters (Japanese and similar) are used. English terms also get singular/plural variants for matching. When the same term appears in several places, title wins, then subtitle, then keywords.
• Keywords-field diagnosis (App Store Connect-connected apps only). Because the field isn’t public, this applies only to connected apps. It is a separate 20-point block that is not added to the app’s 25-point metadata score (src/core/scoring/rules/keywordsField.ts). It breaks down as: using the character budget (8 points), duplicates within the field including English singular/plural pairs (4), overlap with the app name and subtitle (4), generic and category-name terms (2), and wasted spaces after commas or empty entries (2).

These weights and thresholds are ASO Lens’s own, not criteria set by Apple. For example, 90 or more characters earns full marks, stepping down at 75–89 and 50–74, and over 100 scores zero; duplicate and generic-term checks are simple present/absent checks. They are aligned with the things Apple says to avoid — they are not a measurement by ASO Lens of any effect on ranking.

Summary

Apple’s guidance is to fill the 100-character field with comma-separated terms, and not to spend it on words already in the app name, subtitle, or category, or on plurals, generic terms, filler words, or special characters. Apple’s two pages word the limit differently (characters vs. bytes), and don’t spell out full-width commas or Japanese-specific handling. Add keywords per language when you add a localization. Where the documentation is silent, don’t treat folklore as a rule: start with the counter in App Store Connect and Apple’s comma-separated format.