The ASO glossary, in plain English
48 App Store Optimization terms defined without marketing language, with the bit that actually matters in practice. Written for developers, not for a certification exam.
Core concepts
- App Store Optimization
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The full name for ASO — improving how an app ranks and converts in the App Store and Google Play.
Sometimes described as "SEO for apps", though the comparison is loose: app stores index far less text, weigh download and rating behaviour more heavily, and give you no equivalent of backlinks. The levers are metadata, ratings, conversion rate and retention.
See also: ASO
- ASO
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App Store Optimization — the practice of improving an app’s visibility and conversion in app store search and browse.
ASO covers two distinct jobs that are often confused. Visibility is whether your app appears for a search at all, and is driven almost entirely by metadata. Conversion is whether someone who sees you installs, and is driven by your icon, screenshots, ratings and the first lines of your description. Both matter; they need different work and different measurement.
See also: Keyword field, Conversion rate
- Metadata
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The text fields of your store listing that the store reads and, in some cases, indexes for search.
App Store metadata: name (30 characters), subtitle (30), keyword field (100), promotional text (170) and description (4,000). Google Play metadata: title (30), short description (80) and full description (4,000). Which of these are indexed differs by store and determines how you should write them.
See also: Keyword field, Subtitle
- Organic install
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An install that comes from store search or browse rather than paid advertising or an external link.
Organic installs are the output ASO is trying to increase. Both stores report them separately from paid and referral traffic, and the split is the clearest signal of whether ASO work is paying off.
See also: Install velocity
- Store listing
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The public page for your app: name, subtitle, screenshots, description, ratings and reviews.
Everything a user sees before installing. On the App Store the listing includes fields that are indexed for search (name, subtitle, keyword field) and fields that are not (description, promotional text). On Google Play the full description is indexed as well.
See also: Metadata
Keywords
- Head term
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A short, high-volume, heavily contested search term such as "recipe app" or "photo editor".
Head terms are almost always owned by apps with six-figure rating counts and years of download history. Targeting them is the single most common waste of an indie developer’s ASO time. Revisit them when your rating count has grown by roughly an order of magnitude.
See also: Long-tail keyword
- Keyword cannibalisation
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Two of your own apps competing for the same search term, splitting the signal between them.
Common in portfolios where several apps target one niche. Neither app accumulates enough download velocity on the term to break the top ten. The fix is deliberate differentiation of the keyword sets rather than hoping the store sorts it out.
See also: Keyword gap
- Keyword combination
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A multi-word search term you become eligible for because its words appear across your different metadata fields.
Apple builds combinations across the app name, subtitle and keyword field. If "meal" is in your keyword field and "planner" is in your subtitle, you become eligible for "meal planner" without either field containing the phrase. Planning around combinations is where the last twenty per cent of keyword coverage comes from.
See also: Keyword field
- Keyword difficulty
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A 0–100 estimate of how hard it is to reach the top ten for a search term.
Computed from the apps currently ranking: their rating counts, rating velocity, how prominently they use the keyword, and how stable the top ten has been. Difficulty is a property of the keyword alone — whether you can win it depends on your own app, which is what winnability measures.
See also: Winnability, Popularity score
- Keyword field
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A hidden 100-character, comma-separated field in App Store Connect that is indexed for search.
The keyword field is invisible to users and one of the strongest ranking inputs on the App Store. Do not put spaces after commas, use singular forms, never repeat a word already present in your app name or subtitle, and leave out your category name and the word "app". Google Play has no equivalent field.
See also: Keyword combination, Tokenisation
- Keyword gap
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Keywords a competitor ranks for that you do not rank for at all, or rank for far below them.
The fastest form of keyword research, because a competitor sitting at position four for a term has already proved both that it converts and that a top-ten slot is achievable for an app of roughly their size.
See also: Share of search
- Long-tail keyword
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A longer, more specific search term with lower volume and usually much lower competition.
For a small app the long tail is not a consolation prize, it is the strategy. Ten terms where you rank first to third will out-install one head term where you rank #47, because app store traffic collapses steeply with position.
See also: Head term, Search volume
- Popularity score
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Apple’s 0–100 measure of how often an App Store search term is used.
Available through Apple Search Ads and the closest thing to first-party search volume on the App Store. Logarithmic, so differences at the top of the scale are far larger than they appear. Most useful long-tail terms for a small app sit between 5 and 35.
See also: Search volume
- Search volume
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How often a keyword is searched, usually expressed as a 0–100 popularity score rather than an absolute count.
Apple exposes a search popularity score through Search Ads on a 0–100 logarithmic scale — a 60 is many times a 30, not double it. Google Play publishes no equivalent, so Play volume is inferred from demand signals and autocomplete frequency and should be read as an ordering rather than a count.
See also: Popularity score, Keyword difficulty
- Stop word
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A common word such as "the", "and" or "for" that stores ignore when indexing.
Including stop words in the App Store keyword field spends characters on nothing. Both stores discard them for ranking purposes.
See also: Keyword field
- Tokenisation
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How the store splits your metadata text into individual indexable words.
Tokenisation rules vary by language. Latin-script locales split on spaces and punctuation; Japanese, Korean and Chinese do not use spaces and are segmented differently. Comma-separating a transliterated English list into a Japanese keyword field wastes most of it.
See also: Keyword field, Localisation
- Winnability
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Keyword difficulty scored relative to your specific app rather than in the abstract.
Two apps looking at the same difficulty-45 keyword should reach opposite conclusions if one has 50,000 ratings and the other has 300. Winnability compares your rating count, rating velocity, category position and metadata strength against the actual top ten for that term.
See also: Keyword difficulty
Ranking & measurement
- Category rank
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Your app’s position within its store category, separate from keyword search results.
Category and top-chart ranks are driven mainly by download velocity rather than metadata. Tracking them alongside keyword ranks makes it easy to distinguish a category-wide movement from a keyword-specific one.
See also: Top chart
- Install velocity
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The rate at which your app is being installed, especially following searches for a given keyword.
Both stores weigh recent velocity more heavily than lifetime totals. Velocity attributable to a specific keyword is one of the strongest signals for that keyword’s rank.
See also: Organic install, Top chart
- Keyword rank
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Your app’s position in search results for a specific keyword, in a specific country and store.
Measured by querying live store search results rather than modelled. Positions below roughly 200 stop being meaningful because no user scrolls that far, which is why most trackers record anything lower as unranked.
See also: Rank tracking
- Rank tracking
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Recording keyword positions over time so you can tell whether a metadata change worked.
Useful rank tracking requires three things: a baseline recorded before you ship, a consistent time of day for each check, and release markers so rank movement can be attributed to a specific change. Without all three, the chart is decoration.
See also: Keyword rank, Re-indexing
- Re-indexing
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The store re-reading your metadata after a change, before any rank movement can happen.
On the App Store, re-indexing usually completes one to three days after a version goes live. On Google Play it takes a few days to two weeks. Rank then takes a further two to four weeks to stabilise as conversion data accumulates.
See also: Rank tracking
- Top chart
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The Top Free, Top Paid and Top Grossing lists, ranked primarily by recent download and revenue velocity.
Charts are a visibility channel in their own right and are far more volatile than search rank. They respond to bursts of installs rather than metadata quality.
See also: Category rank, Install velocity
Conversion
- App preview video
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A short autoplaying video on the store listing, up to 30 seconds on the App Store.
Preview videos raise conversion for some categories and lower it for others, because an autoplaying video displaces the first screenshot. Worth testing rather than assuming.
See also: Conversion rate
- Conversion rate
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The share of people who see your store listing and go on to install.
Driven by the icon, the first two or three screenshots, the rating and the first two lines of description. Conversion rate is also a ranking signal on Google Play, so creative work is not purely a marketing concern.
See also: Impression, Screenshot caption
- Custom product page
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An alternate App Store listing with different screenshots and text, reachable by its own URL.
Useful for matching a listing to a specific traffic source or campaign. Custom product pages do not affect organic search rank; they exist to improve conversion for traffic you send yourself.
See also: Product page optimization
- Impression
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A single appearance of your app in search results, browse or a chart.
Impressions measure visibility; installs measure the combination of visibility and persuasion. Rising impressions with a flat install count usually means your keywords improved but your creative did not.
See also: Conversion rate
- Product page optimization
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Apple’s built-in A/B testing for icons, screenshots and preview videos.
Known as PPO. Lets you test up to three treatments against the original with traffic split automatically. The Google Play equivalent is called store listing experiments.
See also: Store listing experiment, Custom product page
- Screenshot caption
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The text overlaid on store screenshots, which carries most of their persuasive weight.
Most users read the first two screenshots and nothing else. Captions should state a benefit rather than name a feature. On the App Store screenshot text is not indexed for search; on Google Play it is not indexed either, but it strongly affects conversion, which is a ranking signal.
See also: Conversion rate
- Store listing experiment
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Google Play’s A/B testing for listing text, icons and screenshots.
Play’s experiments cover more of the listing than Apple’s and report statistical confidence directly. Because Play indexes the description, experiments there can affect both conversion and ranking.
See also: Product page optimization
Reviews & ratings
- Rating count
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The total number of ratings your app has received, and the single strongest driver of keyword difficulty.
Both stores treat rating volume as a proxy for quality and popularity. It is the main reason a keyword that is easy for one app is impossible for another, and the slowest signal to move deliberately.
See also: Keyword difficulty, Rating velocity
- Rating prompt
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The in-app dialogue that asks a user to rate your app.
Timing determines the outcome. Prompting after a successful action produces materially better ratings than prompting on launch. Apple limits requests to three per user per year through the official API.
See also: Rating count
- Rating velocity
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How quickly your app is accumulating new ratings.
Velocity tells you where an app is going, where the total tells you where it has been. An app adding 5,000 ratings a month is far harder to displace than one with the same total that stopped growing two years ago.
See also: Rating count
- Review sentiment
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The tone of a review’s text, scored independently of the star rating attached to it.
Star ratings and text sentiment disagree more often than expected, and the disagreement is informative. A four-star review that spends two paragraphs describing a bug is not a four-star signal.
See also: Review theme
- Review theme
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A cluster of reviews that are about the same underlying subject.
Themes group reviews by what they describe rather than which words they use, so "doesn’t sync", "lost my data" and "changes don’t show on my phone" land together. A theme rising in volume while falling in average rating is usually your next bug.
See also: Review sentiment
Localisation
- Locale inheritance
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App Store locales that fall back to another locale’s metadata when not set separately.
English (UK), English (Australia) and several others inherit from English (US) if left blank. Setting them separately gives you additional independent keyword fields targeting the same language — one of the most reliably overlooked wins in App Store metadata.
See also: Localisation, Keyword field
- Localisation
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Adapting your listing to a specific language and market rather than translating it.
Each App Store localisation gets its own 100-character keyword field, which makes localisation a source of additional keyword capacity rather than only a translation task. Play localises per language rather than per country.
See also: Locale inheritance, Storefront
- Storefront
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A country-specific version of an app store, with its own search results and rankings.
The App Store operates a separate storefront for almost every country it sells in. The same keyword can have very different demand and a completely different competitive set in each, so research and rank tracking are both per-storefront.
See also: Localisation
Stores & tooling
- Android vitals
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Google Play’s technical health metrics, principally crash rate and ANR rate.
Poor vitals demonstrably suppress Play visibility. There is no public App Store equivalent, which makes technical quality a more direct ranking concern on Android.
See also: Google Play Console
- App Store Connect
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Apple’s portal for managing app metadata, pricing, releases and analytics.
Where the keyword field lives. Metadata changes to the keyword field require a new version submission, so batch them with a release you were shipping anyway.
See also: Keyword field
- Apple Search Ads
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Apple’s paid placement product for App Store search results.
Separate from organic ASO but connected to it: Search Ads is where Apple exposes its search popularity scores, which makes it a data source even for developers who never buy a placement.
See also: Popularity score
- Google Play Console
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Google’s portal for managing Play listings, releases, experiments and vitals.
Store listing text on Play can be updated without shipping a new bundle, which makes copy iteration faster than on the App Store.
See also: Android vitals
- In-app purchase name
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The display name of an IAP, which is indexed for App Store search.
Free keyword coverage that most developers never claim. Naming subscription tiers with search terms in mind adds indexed text outside your 160-character budget. Not indexed on Google Play.
See also: Metadata
- MCP server
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A Model Context Protocol endpoint that lets AI assistants query a tool’s live data.
An MCP server for an ASO tool means an assistant can answer questions about your actual keywords, ranks and reviews rather than from training data. ASOnest ships one on every paid plan.
See also: ASO
- Promotional text
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A 170-character App Store field that can be changed without submitting a new version.
Not indexed for search. Useful for announcing a sale, a new feature or a fix without going through review. Appears above the description.
See also: Metadata
- Short description
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Google Play’s 80-character summary, indexed for search and displayed above the fold.
The Play field closest in weight to the App Store subtitle. Heavily indexed and prominently displayed, so it deserves the same care as a headline.
See also: Metadata
- Subtitle
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A 30-character App Store field shown under the app name and indexed for search.
The second-heaviest ranking field after the app name. Use it for a keyword cluster distinct from the name — repeating a word between the two wastes the field entirely.
See also: Metadata, Keyword field
Guides that use these terms properly
The complete ASO guide for indie developers
How store search ranks apps, how to pick keywords, and what to write in each field.
The 100-character keyword field
Tokenisation, combinations, and the characters most apps waste.
Keyword difficulty, explained properly
What feeds the score and why the same number means different things.
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