ASO Guidelines

App Store Optimization (ASO) is the practice of tuning your app's metadata so it ranks for the right searches and converts the right users. KAppMaker's ASO tools (text localization and screenshot translation) all enforce the rules on this page. If you write your own metadata by hand, follow them too.

Field character limits

iOS (App Store Connect / Fastlane texts/<locale>/)

File	Limit	Notes
name.txt	30 chars	App name shown on the store. Front-load your strongest keyword (left = stronger ranking weight).
subtitle.txt	30 chars	Single line under the name. Use it for secondary keywords or the value proposition.
keywords.txt	100 chars	Comma-separated, NO spaces after commas. Each comma-separated token is one indexed search term.
description.txt	4000 chars	Conversion copy. Less weighted for search than name/subtitle/keywords.

Android (Google Play / Fastlane playstore_metadata/<locale>/)

File	Limit	Notes
title.txt	30 chars	App title shown on the store. Primary keyword goes here.
short_description.txt	80 chars	Below the title in the store listing. Both indexed AND visible — has to read well AND contain keywords.
full_description.txt	4000 chars	Heavily indexed on Google Play. Use the primary keyword 3–5 times naturally. Bullet lists welcome.

iOS keyword field rules

The keywords.txt file on iOS is special — it's a comma-separated list of indexable tokens that's never shown to users. Optimizing it well is the single highest-ROI ASO win.

1. No word repeats across name, subtitle, and keywords within the same locale. Apple already indexes every word in your name and subtitle. Repeating them in the keywords field wastes your 100-char budget.
2. No spaces after commas. photo,editor,filter is correct; photo, editor, filter wastes 2 chars and produces the same indexing.
3. No brand or app name. Apple indexes the brand from the name field automatically — duplicating it in keywords is wasted space.
4. Avoid plural/singular pairs (runner, runners) unless they unlock genuinely distinct searches.
5. No filler words (app, best, free, new, pro, the, for, with, and). Every slot must be a searchable term users actually type.

Android description rules

1. Primary keyword in title AND short_description. Both fields contribute to ranking; only one of them is visible above the fold on the store page.
2. full_description uses the primary keyword 3–5 times naturally distributed across paragraphs, with 5–10 secondary keywords woven in. Never keyword-stuff — Google penalizes it and users notice.
3. Lead with the user's problem, then the value, then the feature list, then social proof if relevant. Bullet lists are fine and tend to convert well.

Native-feel test (for market localization)

When localizing for a specific market (Mode 2 of localize-metadata), every locale must read as if written by a native marketer in that country. Apply this test to every output:

• Would a native speaker think this was originally written in their language?
• If translated literally from English, are there idioms or word orders that read awkwardly? Rewrite them.
• Are there English loan-words you used? They're fine ONLY if they're standard for that market in your app's category. Otherwise replace them with the native equivalent.
• Does the value proposition resonate with that market's culture? (E.g. "save money" lands harder in some markets, "save time" in others, "look good" in others.)

A literal translation is worse than nothing. It signals "this is a foreign app" and tanks conversion.

Two distribution strategies

Strategy 1 — Keyword Expansion (US-indexed locales)

The US App Store indexes 9 additional locales beyond en-US even when the user's device is set to English. By writing English content into those 9 locale folders with different keywords in each, you multiply the indexed keyword surface — roughly 9× the searchable terms for the same app.

The 9 indexed locales:

iOS folder	Play folder
ar-SA	ar
fr-FR	fr-FR
ko	ko-KR
pt-BR	pt-BR
ru	ru-RU
vi	vi
zh-Hans	zh-CN
zh-Hant	zh-TW
es-MX	es-MX

Trade-off: users in those countries see English copy. For most utility / productivity / global SaaS apps that's acceptable; for B2C consumer apps targeting specific local markets, use Strategy 2 instead.

Strategy 2 — Market Localization (native per-locale)

Write per-locale native copy adapted to local search behavior, locally trending keywords, and the culture's framing of the value proposition. The goal is discoverability + conversion in each individual market — not English-keyword surface in the US.

Use this when you genuinely target multiple countries and want users in each one to see copy that feels written for them.

Pick one, not both

The two strategies conflict — if you've assigned fr-FR to hold "drift coach, lap timer, telemetry" English keywords (Strategy 1), you can't also have it hold native French copy targeting French search terms (Strategy 2). Decide per-app which strategy fits.

KAppMaker's localize metadata skill workflow makes both strategies one-shot operations — see Metadata Localization.

See also

• Metadata Localization — generate localized name/subtitle/keywords/description (iOS) and title/short_description/full_description (Android) files for both strategies above.
• Screenshot Translation — translate marketing screenshots into 48+ locales using fal.ai.