App Store Cross-Localization: How to Double Your Keywords for Free

You have 100 characters in your iOS keyword field. You have carefully optimized every character, stripped duplicates, removed filler words, and packed in as many relevant terms as possible. But what if you could get another 100 characters -- without changing your primary listing, without paying anything, and without any risk of Apple rejection?

Cross-localization is Apple's least-discussed ASO feature. It exploits the fact that Apple indexes metadata from multiple locale configurations for certain country storefronts. By adding a secondary locale to your app in App Store Connect, you gain an entirely separate keyword field that Apple indexes alongside your primary one. This guide explains exactly how it works, which locale pairs to target, and how to implement it step by step.

What Cross-Localization Is and Why It Matters

When a user searches the App Store in a specific country, Apple does not only look at the metadata you set for that country's primary language. For many storefronts, Apple also indexes metadata from one or more secondary locales. This means keywords from both your primary locale and your secondary locale contribute to your search rankings in that country.

The practical impact is significant. Instead of ranking for keywords packed into a single 100-character keyword field plus your 30-character title and 30-character subtitle, you can rank for keywords across two complete sets of metadata. That is potentially 200 characters of keyword fields, 60 characters of titles, and 60 characters of subtitles -- all indexed for the same storefront.

This is not a hack or an exploit. Apple designed its localization system to support multilingual markets. Countries like the United States have large populations that search in both English and Spanish. Canada has English and French speakers. Switzerland has German, French, and Italian. Apple indexes multiple locales for these markets to serve all their users. The ASO opportunity is a side effect of this legitimate design.

The technique requires zero engineering work. You do not need to translate your app's UI, localize your screenshots, or change any code. You only need to add metadata -- title, subtitle, and keyword field -- for a secondary locale in App Store Connect. That is a 15-minute task that can double your keyword coverage.

Which Locale Pairs Cross-Index

Apple's cross-indexing is not random. Each App Store country storefront has a defined primary locale and one or more secondary locales whose metadata also gets indexed. The pairing follows the linguistic demographics of each country.

The key concept is this: if a country's storefront cross-indexes two locales, then keywords from both locales' metadata contribute to search rankings in that country. You do not get to choose which locales cross-index -- Apple determines the pairs based on the country.

For example, the United States storefront indexes both English (US) and Spanish (Mexico) metadata. This means if you add a Spanish (Mexico) localization with a different set of keywords, those Spanish (Mexico) keywords will also help your app rank in searches on the US App Store -- even for users searching in English.

The most powerful pairs are those where you can use the secondary locale to add English keywords (or keywords in the same language as your primary listing). Some developers fill the secondary locale's keyword field with additional English terms rather than actual Spanish or French terms. This works because Apple indexes the raw text regardless of language -- it does not validate that your Spanish (Mexico) keyword field contains actual Spanish words.

However, be thoughtful about the title and subtitle for secondary locales. Users who have their device set to the secondary language will see that locale's title and subtitle. If your Spanish (Mexico) title is gibberish English keywords, Spanish-speaking users in the US will see a broken listing. The keyword field, being invisible to users, is safe to fill with any language.

Complete Table of Known Cross-Localization Pairs

The following table lists the most reliably confirmed cross-localization pairs. The ASO community has validated these through testing, and they have remained stable across multiple years. Apple does not publish this information officially, so minor changes are always possible.

The most valuable rows in this table are the ones where the secondary locale uses a language you already write metadata in. For a primarily English app, the US + Spanish (Mexico) pair is the highest-impact opportunity because the US is the largest English-language App Store market and the secondary locale gives you a full extra set of metadata fields.

Switzerland is notable for indexing up to four locales. If your app is available in Switzerland, you can potentially set up German, French, Italian, and English metadata -- quadrupling your keyword coverage for that market.

Note that some countries like the UK and Australia appear to only index a single locale. For these markets, cross-localization does not provide additional keyword space, so focus your efforts on the markets that support it.

Step-by-Step Setup in App Store Connect

Adding Secondary Locale Metadata

1. Open App Store Connect and navigate to your app.
2. Select the version you are editing (or your general App Information page for fields that do not require a new version).
3. In the left sidebar, look at the list of localizations. You will see your primary locale listed.
4. Click the "+" button or "Add Localization" option.
5. Select the secondary locale from the dropdown. For the US market, select "Spanish (Mexico)."
6. App Store Connect will create a new localization section with empty fields: title, subtitle, keyword field, description, promotional text, and what's new.

You do not need to fill in every field. The minimum for cross-localization purposes is the keyword field. However, if Spanish-speaking users in the US might see this listing, consider providing a real Spanish title and subtitle for a professional appearance.

The description field in the secondary locale does not impact iOS keyword rankings (Apple does not index descriptions for search), so you can leave it as a copy of your English description or provide a translated version for conversion purposes.

Filling in Secondary Locale Keywords

Once the secondary locale is created, the keyword field is your priority. This is where the cross-localization benefit lives.

Open the keyword field for your secondary locale and treat it as a completely fresh 100 characters. Do not copy your primary locale's keywords -- that would defeat the entire purpose. Instead, fill it with the next tier of keywords that did not fit in your primary locale's 100 characters.

Follow the same formatting rules as your primary keyword field: commas without spaces, no duplicates from the secondary locale's own title or subtitle, no plurals, no articles. The only additional rule is: do not duplicate keywords that are already in your primary locale's keyword field, title, or subtitle. Apple cross-indexes both locales, so duplicating across locales is as wasteful as duplicating within a single locale.

Strategy: Using Secondary Locale Keyword Fields for Additional Terms

The optimal strategy treats your primary and secondary locale keyword fields as two halves of a single 200-character keyword budget.

Primary locale keyword field (100 characters): Your highest-priority keywords. These are the terms with the best combination of search volume, relevance, and achievable competition. A solid keyword research strategy will help you rank candidates by these criteria. This is also where you put any keywords that might be time-sensitive or that you want to iterate on frequently.

Secondary locale keyword field (100 characters): Your second tier of keywords. These are terms that did not make the cut for the primary field -- still relevant, still searched, but either slightly lower volume or slightly more competitive. Also a good place for:

• Long-tail keywords that cost too many characters for the primary field
• Synonyms and alternative phrasings of your primary keywords
• Adjacent category terms that broaden your discoverability
• Misspellings of common search terms (if they have real volume)

Think of it this way: if you had a candidate list of 30 keywords sorted by priority, your primary locale gets keywords 1-13 (assuming ~100 characters), and your secondary locale gets keywords 14-26. Both sets are indexed for the same storefront. Instead of your app appearing in searches for 13 keyword roots, it appears for 26.

For your title and subtitle in the secondary locale, you have two approaches:

Approach 1 (Conservative): Provide a legitimate translation of your title and subtitle. This ensures Spanish-speaking users see a proper listing. The translated words also get indexed, adding even more keyword coverage in a different language.

Approach 2 (Aggressive): Use the secondary locale's title and subtitle for additional English keywords that did not fit in your primary title and subtitle. This maximizes English keyword coverage but risks looking unprofessional to users who see the secondary locale listing. Only do this if the secondary locale's language has very few users in that market.

For most developers, Approach 1 is the right call. The keyword field alone gives you 100 extra characters, which is the primary win. The title and subtitle add modest incremental value that is not worth the conversion risk of a broken-looking listing.

What NOT to Put in Cross-Localized Fields

Avoid Duplicating Primary Locale Keywords

This is the cardinal rule of cross-localization. If a keyword is already in your primary locale's title, subtitle, or keyword field, do not repeat it in the secondary locale's keyword field. Apple does not give extra ranking weight for duplicate keywords across locales. Every duplicate is a wasted keyword slot.

Before filling the secondary locale, create a master list of every keyword already covered by your primary locale:

1. List all words from your primary title
2. List all words from your primary subtitle
3. List all terms from your primary keyword field
4. Remove all of these from your secondary locale candidate list

Only then fill the secondary keyword field with the remaining candidates. This ensures zero overlap and maximum coverage.

Avoid Irrelevant Foreign-Language Keywords

Some developers get creative and stuff the secondary locale's keyword field with high-volume Spanish (or French, or German) keywords that have nothing to do with their app. The logic is: more keywords equals more visibility.

This backfires in two ways. First, users who find your app through an irrelevant keyword will see a listing that does not match their search intent. They will not download, or worse, they will download and immediately uninstall. Both behaviors send negative signals to Apple's algorithm, potentially hurting your rankings for the keywords you actually care about.

Second, Apple has become increasingly sophisticated at detecting keyword stuffing. While they do not currently reject apps for mismatched secondary locale keywords, the risk of policy enforcement increases over time. Keeping your secondary locale keywords relevant and honest is both safer and more effective.

The cleanest approach: use the secondary keyword field for English keywords that are relevant to your app but did not fit in your primary field. If you want to also reach Spanish-speaking users, add genuinely relevant Spanish keywords as well.

How Android Handles This Differently

Google Play does not cross-index locales. Each localization on Google Play only affects rankings in the specific storefront for that language and country. If you set up a Spanish localization for the US Play Store, those Spanish keywords only help you rank when users search in Spanish on Google Play -- they do not contribute to English search rankings.

This means cross-localization is an iOS-exclusive technique. Android developers cannot double their keyword coverage through locale tricks. Instead, Android ASO focuses on embedding keywords in the description (which Google indexes, unlike Apple) and optimizing per-market localizations independently.

If you ship on both platforms, treat cross-localization as an iOS-only advantage. Your Android ASO strategy should focus on description keyword density, backlinks, and user engagement signals -- the levers that Google actually weighs.

Measuring the Impact of Cross-Localization

Tracking New Keyword Rankings

After implementing cross-localization, give Apple 1-2 weeks to index your new keywords. Apple's indexing cycle for metadata changes is typically 24-72 hours, but it can occasionally take longer, especially for newly added locales.

Once the indexing period passes, check rankings for the keywords you added to the secondary locale:

Manual check: Search each new keyword in the App Store on a device set to the primary country. If your app appears in results for a keyword that only exists in your secondary locale's keyword field, cross-indexing is confirmed and working.

Search Ads validation: Check whether Apple's Search Ads tool suggests your new secondary keywords when you look up your app. If they appear as suggested keywords, Apple has indexed them.

Impression monitoring: In App Store Connect analytics, watch for an increase in search impressions. You cannot isolate which keywords drive which impressions, but a meaningful uptick in the weeks following cross-localization indicates expanded keyword coverage.

Monitoring Download Changes

The ultimate metric is organic downloads. In App Store Connect, check your Impressions and Product Page Views from App Store Search sources. Compare the 30 days before cross-localization to the 30 days after.

Realistic expectations: cross-localization typically produces a 10-30% increase in keyword-driven impressions. The download impact depends on how competitive your new keywords are and how well your listing converts. For apps with already-strong conversion rates, more impressions translate directly into more downloads.

If you are not seeing an impact after 3-4 weeks, audit your secondary keyword field. Common issues include: duplicating primary locale keywords (no incremental value), targeting extremely competitive terms (you rank too low to get impressions), or targeting terms with very low search volume (impressions exist but are negligible).

Real Example with Before/After Keyword Count

Consider a productivity app called "TaskFlow - To Do List" with the subtitle "Organize Your Day Simply." The app targets the US App Store.

Before cross-localization (English US only):

Primary title words indexed: taskflow, to, do, list Primary subtitle words indexed: organize, your, day, simply Primary keyword field (100 characters):

planner,remind,schedule,project,manage,team,deadline,priority,kanban,habit,goal,calendar,note,focus

Total unique keywords contributing to ranking: ~22 terms (8 from title/subtitle + 14 from keyword field).

After cross-localization (English US + Spanish Mexico):

Everything above stays the same. Now add Spanish (Mexico) localization:

Secondary title: "TaskFlow - Lista de Tareas" (legitimate Spanish translation) Secondary subtitle: "Organiza Tu Dia Facilmente" Secondary keyword field (100 characters):

checklist,agenda,assign,sprint,board,pomodoro,timer,track,daily,weekly,routine,workflow,task,plan,tag

New title words indexed (Spanish): lista, tareas, organiza, tu, dia, facilmente New keyword field words: 15 additional English terms

Total unique keywords contributing to ranking: ~43 terms (22 original + 6 Spanish title/subtitle + 15 new keyword field). That is nearly double the keyword coverage with 15 minutes of work in App Store Connect.

The secondary keyword field adds terms like pomodoro, sprint, board, and workflow that were relevant but did not make the cut for the primary 100 characters. Now they are all indexed and contributing to search visibility.

Over 30 days, an app implementing this strategy can expect to appear in search results for significantly more queries. Even if each new keyword contributes only a handful of additional impressions per day, 15 new keywords at 5-10 impressions each adds up to 75-150 daily impressions -- a meaningful expansion for an indie app.

Risks and Apple Guideline Compliance

Is Cross-Localization Against Apple's Rules?

No. Cross-localization uses Apple's localization system exactly as designed. Apple explicitly supports adding multiple localizations for your app, and the cross-indexing behavior is a feature of how their search algorithm works, not a loophole.

Apple's App Store Review Guidelines (Section 2.3.7) state that metadata should accurately represent the app's content. As long as your secondary locale metadata honestly describes your app -- which it will, if you are using relevant keywords -- there is no guideline conflict.

Developers have been using cross-localization since at least 2016, and Apple has never issued guidance against it or penalized apps for implementing it. The technique is widely documented in the ASO community and used by apps of all sizes, from indie projects to Fortune 500 companies.

Potential Pitfalls

While cross-localization itself is safe, there are edge cases to be aware of:

Apple may change cross-indexing pairs. Apple occasionally adjusts which locales cross-index for specific countries. A pair that works today might change in a future update. This is rare but not impossible. Monitor your secondary keyword rankings periodically and be prepared to adjust.

Spammy secondary metadata may trigger review. If your secondary locale's title and subtitle look like keyword-stuffed nonsense rather than a legitimate localization, Apple's review team might flag it. Keep your visible fields (title, subtitle) professional. The keyword field, being invisible, has more flexibility.

Conversion impact on secondary-language users. If your app's UI is English-only but your secondary locale has a Spanish title, Spanish-speaking users who land on your listing might expect a Spanish app. When they realize the app is only in English, they may not download -- or worse, download and leave a negative review. If this concerns you, add a note in the secondary locale description clarifying the app's available languages.

Do not over-optimize at the expense of user experience. The goal of cross-localization is expanded keyword coverage, not keyword spam. Every term in your secondary keyword field should be a legitimate descriptor of your app. This keeps you compliant with Apple's guidelines and ensures that any new users you attract through expanded keywords actually find value in your app.

Key Takeaways

• Cross-localization lets you rank for up to 200 characters of keywords in a single country storefront by adding a secondary locale.
• Apple cross-indexes specific locale pairs per country. The US indexes English (US) + Spanish (Mexico), Canada indexes English + French, and most European countries index their primary language + English (UK).
• Fill the secondary locale keyword field with entirely different keywords than your primary locale. Zero overlap.
• Keep the secondary locale's title and subtitle professional -- users with that language setting will see them.
• The keyword field is invisible to users, so it is safe to fill with English terms even in a non-English locale.
• Google Play does not cross-index locales, making this an iOS-exclusive technique.
• Expect 10-30% more keyword impressions after implementation. Measure after 2-4 weeks.
• This is not against Apple's rules. It uses Apple's localization system as designed.

Cross-localization is the closest thing to a free lunch in ASO. Fifteen minutes in App Store Connect, zero code changes, zero cost, and you can nearly double the number of keywords your app ranks for. If you have already optimized your primary keyword field and want more coverage, this is the next move.

StoreLit's keyword gap analysis can help identify which keywords to put in each locale by showing you exactly which competitor terms you are missing -- giving you a data-driven candidate list for both your primary and secondary keyword fields.