Keyword Field

Definition

The Keyword Field is a hidden metadata field (invisible to users) where developers enter keywords for search indexing. It exists on the Apple App Store (100 characters) and Amazon Appstore (no documented character limit, but recommendations suggest keeping it concise). Google Play has no keyword field — it relies on Full Description text for keyword indexing instead.

The Keyword Field is one of the three primary indexed fields on iOS (alongside App Title and Subtitle) and is the most technically optimizable field in ASO — every character matters.

How It Works

Apple App Store

Specifications:

• Limit: 100 characters total (including commas)
• Format: Comma-separated keywords, NO spaces after commas
• Visibility: Hidden from users (only visible to developer in App Store Connect)
• Indexing weight: High (third after title and subtitle, but provides the most keyword real estate)

Combinatorial matching (critical concept):

Apple creates indexed phrases by combining words from Title + Subtitle + Keyword Field. This is the single most important optimization mechanic:

Title: "PhotoApp - Editor"
Subtitle: "Filters & Collage Maker"  
Keywords: "retouch,background,remove,portrait,selfie,crop,adjust,beauty,skin"

The algorithm automatically indexes combinations like:

• "photo editor" (title words)
• "photo filter" (title + subtitle)
• "photo retouch" (title + keywords)
• "collage maker" (subtitle words)
• "selfie editor" (keywords + title)
• "background remove" (keywords + keywords)
• And many more permutations...

Optimization rules:

1. No spaces after commas — "photo,editor" = 12 chars. "photo, editor" = 13 chars. Saving 1 char per comma adds up.
2. No plurals — Apple indexes both singular and plural forms automatically. "game" covers "games."
3. No words already in title or subtitle — they're already indexed. Repeating wastes characters.
4. No stopwords — "the," "and," "or," "a," "an" are ignored by the algorithm.
5. No competitor brand names — may trigger app rejection.
6. No "app," "free," "iPhone," "iPad," "new," "best" — Apple strips these as generic/device terms.
7. Single words preferred — enter "photo" and "edit" separately rather than "photo editor" — combinatorial matching handles the phrase.
8. Numbers are indexed — "365" is a valid keyword.

Efficiency target: 14+ unique keywords in 100 characters.

Example — Before (inefficient, 89 chars, 8 keywords):

task manager, todo list, productivity app, daily planner, reminder app

Example — After (optimized, 97 chars, 14 keywords):

task,todo,checklist,reminder,organize,daily,planner,schedule,deadline,goals,habit,widget,sync,team

Amazon Appstore

• Amazon also provides a Keywords Field for search targeting
• No documented hard character limit, but brevity recommended
• Comma-separated format
• Keywords indexed for both text and voice search (Alexa on Fire devices)
• Less documentation on combinatorial matching mechanics
• Feature Bullets provide additional keyword surface area

Google Play Store

• No keyword field exists — Google relies on App Title, Short Description, and Full Description for keyword extraction
• Developers must embed keywords naturally in descriptive text

Formulas & Metrics

Keyword Field Efficiency:

Efficiency = Unique_Keywords_Indexed / Character_Limit × 100%

Characters per keyword (target):

Avg_Chars_Per_Keyword = Characters_Used / Number_of_Keywords

Target: <7 chars/keyword (including comma separator). This means favoring shorter keywords.

Optimization checklist score:

• All 100 characters used
• No spaces after commas
• No words from title or subtitle
• No plurals
• No stopwords or generic terms
• No competitor brand names
• Single-word entries (not phrases)
• Prioritized by Search Volume × Keyword Relevance

Best Practices

1. Fill all 100 characters — leaving 10 unused characters wastes ~10% of your keyword potential.

1. Prioritize by Search Volume × Relevance — put your highest-value keywords first (though position within the field doesn't affect weight, it enforces discipline).

1. Re-optimize with each update — keyword trends change seasonally. Review and refresh the keyword field every 4-8 weeks.

1. Use ASO tools for keyword suggestions — AppTweak, Sensor Tower, MobileAction can suggest keywords based on competitor analysis and search data.

1. Monitor indexing status — after updating, use ASO tools to verify which keywords your app is actually indexed for. Not all entered keywords may index.

1. Consider combinatorial potential — choose keywords that create valuable multi-word combinations with your title and subtitle words.

1. Test keyword rotation — swap out low-performing keywords (ranked #50+) for new candidates each update cycle.

Dependencies

Influences (this term affects)

• Keyword Indexing (iOS) — keyword field is a primary source for the index
• Relevance Score — field keywords contribute to relevance scoring
• Search Visibility — more keywords indexed = broader visibility
• Search Result Ranking — keyword presence affects ranking eligibility
• Custom Product Pages (CPP) — CPP keywords must come from the keyword field

Depends On (affected by)

• Keyword Research — research determines which keywords to include
• App Title — title words should NOT be repeated in keyword field
• Subtitle — subtitle words should NOT be repeated in keyword field
• Search Volume — prioritize keywords with sufficient search volume
• Keyword Difficulty — balance high-volume with achievable difficulty
• Apple Search Algorithm — algorithm determines how field is processed

Platform Comparison

Related Terms

• App Title
• Subtitle
• Short Description
• Full Description
• Keyword Research
• Keyword Indexing (iOS)
• Metadata Optimization
• Search Volume
• Keyword Difficulty

Sources & Further Reading

• Apple: App Store Connect Keyword Guidelines
• ZeePalm: iOS Keyword Optimization Guide (2024)
• Stormy AI: iOS Keywords Playbook (2025)
• ASOMobile: Text Optimization for App Store