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ASO Glossary

Plain-language definitions of the App Store Optimization terms that actually move installs — written by the team that does this for funded app startups every day. 50 terms and growing.

Foundations

App Store Optimization (ASO): Is the practice of improving an app's visibility and conversion in app store search and browse so it earns more organic installs without paying per download.

App Store mechanics

Cross-Localization: Is the app store behavior where a single country storefront indexes keywords from more than one localization — letting you rank for extra terms by filling secondary localizations users in that country never see.
Localization: Is adapting an app's store listing — metadata, screenshots, and keywords — to a specific language and market so it ranks and converts in that audience's own language.
Storefront: Is a single country or region's version of the app store, with its own charts, search rankings, featuring, and set of indexed localizations.
Primary Localization: Is the default language of a storefront — the metadata most users in that country see, and the first localization the app store indexes for keyword search there.
Secondary Localization: Is an additional localization whose keyword field the app store also indexes in a storefront — giving you extra keyword coverage that most users in that country never see.
App Category: Is the store classification you assign your app, which sets the charts and browse lists it competes in and influences which searches it surfaces for.

Metadata

Keyword Field: Is the app store's hidden 100-character metadata field where you list comma-separated keywords that count toward search ranking but are never shown to users.
App Title (App Name): Is the most heavily weighted ranking field on both stores — up to 30 characters on the app store — where your brand name and single most valuable keyword belong.
Subtitle: Is the app store's 30-character line beneath the app name — the second-strongest ranking field and a key conversion hook on the product page.
Promotional Text: Is a 170-character app store field above the description that you can update anytime without a new app release — but it does not affect keyword ranking.
App Description: Is the long-form text on a store listing — on google play it directly affects keyword ranking, while on the app store it is conversion-only and not indexed for search.
Metadata Character Limits: Are the fixed maximum lengths apple and google enforce on each listing field — exceed them and your text is silently truncated at submission.
Metadata: Is the collection of text fields — app name, subtitle, keyword field, description and more — that tell a store what your app is and which searches it should appear for.

Discovery & ranking

App Store Search Algorithm: Is the system that ranks apps for a search query based on keyword relevance in metadata combined with performance signals like downloads, conversion, and ratings.
Ranking Factors: Are the inputs an app store uses to order search and chart results — split between on-metadata relevance signals and off-metadata performance signals.
Keyword Difficulty: Is a score estimating how hard it is to rank on the first page for a keyword, based on the strength and competition of the apps already ranking for it.
Search Volume (Popularity Score): Is an estimate of how often users search a keyword — apple expresses it as a 5–100 popularity score, and it tells you the traffic a top ranking could deliver.
Long-Tail Keyword: Is a longer, more specific multi-word search phrase with lower volume but higher intent and lower competition — often the fastest path to first-page rankings for a new app.
Branded Keyword: Is a search term containing a brand or app name — either your own (protecting it) or a competitor's (bidding or ranking against it).
Keyword Stuffing: Is overloading metadata with repeated or irrelevant keywords in a way that reads unnaturally, wastes ranking weight, and can trigger store rejection or hurt conversion.
Keyword Rank: Is your app's position in the search results for a specific keyword in a specific storefront — the core metric aso is judged by.
Browse vs. Search: Are the two organic discovery paths in an app store — search (users typing a query) and browse (charts, categories, and editorial featuring) — which reward different optimizations.
Category Ranking: Is your app's position within its app store or google play category chart, driven mainly by download velocity and a strong browse-discovery surface.
Install Velocity: Is the rate at which an app gains downloads over a short window — a momentum signal the store algorithms read as evidence that an app deserves higher ranking.
Search Suggestions (Autocomplete): Are the queries an app store proposes as a user types in the search bar, ordered roughly by popularity — a free, real-time read on what people actually search for.
Keyword Indexing: Is whether a store has registered your app as eligible to appear for a given term — if a keyword isn't indexed, you can't rank for it no matter how relevant you are.
Top Charts: Are the ranked lists of the most-downloaded apps by category and country, a high-traffic browse surface driven mainly by recent install velocity.
Search Popularity Score: Is a measure of how often a keyword is searched — surfaced on a roughly 5-to-100 scale in apple search ads — used to judge whether a term is worth targeting.
Competitor Keyword Analysis: Is the practice of studying which keywords rival apps rank for to find high-value terms you're missing — the basis of a keyword gap analysis.

Metrics

Impressions: Count how many times your app listing or icon was shown to users across search, browse, and referrals — the top of the aso funnel before taps and installs.
Organic Installs: Are app downloads that come from unpaid discovery — search, charts, browse, featuring, and referrals — rather than from paid advertising.
Tap-Through Rate (TTR): Is the share of people who, after seeing your app in search or browse results, tap through to open its product page — the app store's version of click-through rate.
Retention Rate: Is the percentage of users still active a set number of days after install — a quality signal both app stores increasingly weigh when deciding how to rank an app.
Cost Per Install (CPI): Is the average amount you pay to acquire one install through paid channels — the benchmark organic aso is measured against.
Product Page Views: Are the number of times users open your app's full store listing — the middle of the conversion funnel, between impressions and installs.

Conversion

Conversion Rate (CVR): Is the share of users who install your app after viewing its listing — the single metric that turns visibility into installs and feeds back into ranking.
Screenshots: Are the listing's primary conversion asset — the visual story of your app that shoppers scan in seconds and that does most of the work of earning an install.
App Preview (Video): Is the short autoplaying video on a store listing that demonstrates the app in motion — a strong conversion lever when it shows real value in the first few seconds.
App Icon: Is the small square mark that represents your app everywhere it appears — the first impression in search and browse, and a meaningful conversion and tap-through driver.
Ratings & Reviews: Are the star score and written feedback on your listing — a top conversion driver and a ranking signal, where both the average and the volume and recency matter.
Conversion Funnel: Is the path a user takes from seeing your app to installing it — impression, to product-page view, to download — where each step has its own drop-off to diagnose and fix.
A/B Testing: Is running two or more versions of a store-listing element against live traffic to measure which converts better — replacing opinion with data.

Apple features

Product Page Optimization (PPO): Is apple's native a/b testing feature that lets you test up to three variant treatments of your icon, screenshots, or app preview against the default and measure conversion.
Custom Product Pages (CPP): Are additional app store product pages — up to 35 — each with its own screenshots, preview, and promotional text, reachable by unique urls to match specific audiences or campaigns.
Apple Search Ads (ASA): Is apple's paid search advertising platform that places sponsored app results at the top of app store search — a paid channel that complements organic aso.
In-App Events: Are timely, time-limited happenings inside your app — like a tournament, premiere, or challenge — that apple lets you surface as discoverable event cards across the app store.
Today Tab: Is the app store's editorial home screen, where apple's team features apps through stories and curated lists — an earned placement that drives large, ranking-boosting install spikes.

Google Play features

Custom Store Listings (Google Play): Are google play's audience-targeted listing variants that show different metadata and creative to specific countries, install states, pre-registration users, or ad campaigns.
Store Listing Experiments (Google Play): Are google play's built-in a/b testing tool for comparing listing variants — icon, screenshots, text, and more — against the current default to find what converts best.

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