iOS Keyword Field: Rules, Character Limits & Optimization

The iOS keyword field is 100 characters of hidden, indexed text that can make or break your App Store visibility. It's one of only three text fields Apple indexes for search — alongside your title and subtitle — yet most developers either waste it with duplicate words, fill it incorrectly, or leave characters unused. This guide covers every rule, every trick, and every optimization strategy for the iOS keyword field so you extract maximum value from every single character.

What Is the iOS Keyword Field?

The keyword field is a metadata field in App Store Connect that Apple's search algorithm indexes to determine which search queries your app is relevant for. Unlike your title and subtitle, the keyword field is never shown to users — it's purely an algorithmic input.

Key specs

• Character limit: 100 characters
• Format: Comma-separated values
• Visibility: Hidden from users (only visible in App Store Connect)
• Indexing: Combined with title and subtitle as a unified keyword set
• Update frequency: Changes take effect with each new app version submission

The Rules: What Apple Allows and Doesn't

Do's

1. Use commas to separate keywords. Each keyword or short phrase should be separated by a comma.
2. Use singular forms. Apple automatically matches both singular and plural. "tracker" matches both "tracker" and "trackers."
3. Fill all 100 characters. Every unused character is wasted discovery potential.
4. Include relevant terms only. Keywords must relate to your app's functionality and content.
5. Use numbers where relevant. "2026" or "365" can be valid keywords if users search for them in your context.

Don'ts

1. Don't repeat words from your title or subtitle. Apple indexes title + subtitle + keyword field as a combined set. Repeating "budget" in both your title and keyword field wastes characters.
2. Don't include your app name. Apple already indexes it separately.
3. Don't include your category name. It's automatically associated with your app.
4. Don't use the word "app." Apple adds this implicitly.
5. Don't add spaces after commas. Spaces count against your 100-character limit. Use tracker,budget,expense not tracker, budget, expense.
6. Don't use special characters. Stick to letters, numbers, and commas.
7. Don't include competitor brand names. Apple may reject your submission or remove the keywords. While enforcement is inconsistent, it's a policy violation.
8. Don't use irrelevant terms. High-volume keywords that don't match your app can trigger review flags and tank your conversion rate.

Character Counting: Getting to Exactly 100

Every character matters. Here's how to count correctly:

• Letters and numbers: 1 character each
• Commas: 1 character each (required separators)
• Spaces after commas: 1 wasted character each (don't use them)

Example calculation

tracker,budget,expense,money,spending,finance,planner,savings,bills,income

This is 73 characters — you still have 27 characters to fill. Don't stop here. Add more relevant keywords:

tracker,budget,expense,money,spending,finance,planner,savings,bills,income,weekly,monthly,report,csv

That's 99 characters. You could add one more single-character keyword or adjust to hit exactly 100.

Pro tip: use a character counter

Don't rely on manual counting. Use a character counter tool or a simple script to verify you're using exactly 100 characters. Many ASO tools include a keyword field character counter.

Optimization Strategies

Strategy 1: Keyword deduplication across fields

Before filling your keyword field, list all the words already in your title and subtitle. These are already indexed — never repeat them.

Example:

• Title: BudgetPal - Expense Tracker (words indexed: budget, pal, expense, tracker)
• Subtitle: Smart Money Manager (words indexed: smart, money, manager)

Your keyword field should NOT include: budget, pal, expense, tracker, smart, money, manager. That frees up significant space for new keywords.

Strategy 2: Word combination leveraging

Apple's algorithm combines individual words from your keyword field with words from your title and subtitle to form compound search queries.

If your title contains "budget" and your keyword field contains "planner," Apple can match the search query "budget planner" — even though that exact phrase appears nowhere in your metadata.

This means you should think in terms of individual word components, not complete phrases:

Instead of: budget planner,expense tracker,money manager
Use: planner,savings,bills,income,weekly,monthly (since budget, expense, tracker, money, and manager are already in title/subtitle)

Strategy 3: Synonym and variant coverage

Users search using different words for the same concept. Cover as many relevant synonyms as possible:

• Expense: cost, spending, payment, charges
• Budget: finance, money, savings
• Track: monitor, log, record, manage
• App types: calculator, organizer, planner, helper, assistant

Strategy 4: Misspelling targeting

Common misspellings can be worth targeting if they have search volume:

• "calender" vs "calendar"
• "reciepe" vs "recipe"
• "excercise" vs "exercise"

Apple does handle some common misspellings automatically, but covering frequent ones can capture additional traffic. Use sparingly — prioritize correctly spelled high-value keywords.

Strategy 5: Action and intent keywords

Users often search with action verbs that signal download intent:

• How-to keywords: learn, how, guide, tutorial
• Action keywords: track, manage, plan, organize, scan, edit, create
• Need keywords: best, free, easy, fast, simple, top

Include relevant action keywords that match how users describe their need.

Cross-Locale Keyword Strategy

This is one of the most powerful and underutilized ASO techniques for iOS.

How cross-locale indexing works

Apple indexes keywords from multiple locales for each storefront. For example, the US App Store indexes keywords from:

• English (US) — your primary locale
• Spanish (Mexico) — secondary locale indexed for US store

This effectively gives you 200 characters of keyword space for the US store instead of 100.

How to implement

1. Set up your primary keywords in English (US) locale.
2. Go to Spanish (Mexico) locale in App Store Connect.
3. Fill the Spanish (Mexico) keyword field with additional English keywords that didn't fit in your primary field.

These English keywords entered in the Spanish (Mexico) locale will be indexed for users searching in English on the US App Store.

Locale combinations by storefront

Research the full locale indexing matrix for every market you target. Some markets index 3-4 locales.

The Keyword Field Optimization Process

Step 1: Build your master keyword list

Compile every relevant keyword from:

• Brainstorming sessions
• Competitor analysis (what keywords do they rank for?)
• Auto-suggest results from the App Store
• User reviews (language users naturally use)
• Your ASO tool's keyword suggestions

Step 2: Score and prioritize

For each keyword, assess:

• Volume: How many people search for this term?
• Difficulty: How competitive is this keyword?
• Relevance: Does it accurately describe your app?
• Current ranking: Are you already ranking? (If so, it might not need to be in the keyword field)

Step 3: Eliminate duplicates

Remove any words already in your title or subtitle. Remove any words Apple adds automatically (app name, category).

Step 4: Prioritize by character efficiency

Calculate the "value per character" of each keyword:

• High-volume, short keywords = high efficiency (e.g., "log" = 3 chars, decent volume)
• Low-volume, long keywords = low efficiency (e.g., "organization" = 12 chars, low volume)

Step 5: Fill the field

Place your highest-priority keywords first (in case Apple gives slight weight to earlier positions — debated but possible). Fill to exactly 100 characters.

Step 6: Submit and track

After updating your keywords with a new app version:

• Wait 2-4 weeks for rankings to stabilize
• Track ranking changes for all target keywords
• Identify which new keywords you're ranking for
• Note which keywords didn't move the needle

Step 7: Iterate

Every update cycle is an opportunity to optimize:

• Drop keywords with no ranking impact after 2-3 cycles
• Add new keywords discovered through competitor analysis or search trends
• Adjust based on seasonal search patterns

Common Keyword Field Mistakes

1. Using spaces after commas. This is the most common mistake. budget, expense, tracker wastes 2 characters on spaces. Use budget,expense,tracker.

2. Repeating title/subtitle words. If "budget" is in your title, putting it in the keyword field accomplishes nothing except wasting 6 characters.

3. Including "app" or your category. Apple already knows your app is an app. Don't waste 3 characters on "app."

4. Using plural forms. Apple matches singular to plural automatically. "trackers" wastes one character compared to "tracker."

5. Targeting irrelevant high-volume keywords. "Instagram" has huge volume, but unless your app is related to Instagram, it won't help you — and it may trigger a review rejection.

6. Not filling all 100 characters. Leaving characters unused is leaving potential visibility on the table.

7. Never updating keywords. Search trends change. Competitors shift strategies. Your keyword field should be refreshed at least monthly.

Real-World Example: Before and After

Before (poor optimization — 76 characters, 24 wasted)

Title: MoneyTrack - Budget App
Subtitle: Track Your Expenses
Keyword field: budget app, expense tracker, money manager, finance, budget planner

Problems:

• "budget" repeated from title (6 chars wasted)
• "app" included (3 chars wasted)
• "expense" and "tracker" repeated from subtitle (14 chars wasted)
• Spaces after commas (5 chars wasted)
• Only 76 characters used

After (optimized — 100 characters, zero waste)

Title: MoneyTrack - Budget App
Subtitle: Track Your Expenses
Keyword field: spending,savings,planner,bills,income,receipt,monthly,weekly,financial,log,personal,organizer,simple

Improvements:

• Zero duplicate words from title/subtitle
• No spaces after commas
• All 100 characters used
• 13 unique additional keywords indexed
• Combined with title/subtitle, the app now targets 20+ keyword combinations

How Appalize Helps with Keyword Field Optimization

Appalize streamlines your keyword field optimization workflow:

• Keyword suggestions — Discover high-opportunity keywords you haven't considered, with volume and difficulty data.
• Competitor keyword analysis — See which keywords your competitors rank for and identify what you're missing.
• Keyword tracking — Monitor ranking changes after each keyword field update to measure impact.
• Character counter — Built-in tools to optimize your 100-character keyword field without wasting space.

Stop guessing which keywords to include. Use Appalize to make data-driven keyword decisions and track every ranking change.

Conclusion

The iOS keyword field is only 100 characters, but it's one of the most impactful 100 characters in your entire marketing strategy. Every character you waste on duplicates, spaces, or irrelevant terms is a missed opportunity to appear in a search that could have driven a download.

Master the rules first: no duplicates, no spaces after commas, singular forms, fill all 100 characters. Then layer in advanced strategies: cross-locale indexing for bonus keyword space, word combination leveraging, and systematic iteration based on ranking data.

The developers who treat their keyword field as a living document — testing, measuring, and refining with every update — are the ones who steadily climb the rankings. The ones who set it once and forget about it are the ones wondering why their competitors keep showing up above them.