17 July, 2019

App Store Optimization Guide 2019 – ASO for iOS

ASO for iOS

With competition growing by the second, standing out from the crowd is a challenge in today’s app stores. The iTunes App Store became the second largest store with an estimated 2.2 million apps available for download by the end of Q3 2018. Revenues from the App Store are projected to reach $189 billion USD by 2020.

Taking all of that into consideration, it’s time to better understand how to best optimize your app in the App Store.

In this article, we will explain the major elements of your app’s store listing that need ASO attention in order to achieve your app’s full organic growth capability.

At yellowHEAD, we have perfected our approach to iOS ASO and focus on 4 major aspects: search optimization, conversion, explore optimization, and tracking & monitoring.

Table of Contents:

App Search Optimization:

Search optimization is nothing new in our modern-day world of “just Google it!” Understanding how the Apple’s App Store search algorithm works is a vital part in making sure your app to stays away from becoming ‘virtually invisible’ – the black hole of ASO where apps are never to be found.

In this section, we will explain the key elements of iOS search visibility optimization for anyone looking to better understand ASO.

Metadata Rules:

*Metadata is the content we choose to publish that describes our app

When creating your app’s store listing, keep in mind that Apple limits both the written content we choose and the length of the content.

The App Store has gone through changes over the years and although we may still see some outliers here and there, as of the beginning of 2019 the following metadata rules are in effect.


An app title is limited to a 30-character space (including spaces between words). In the eyes of the search algorithm, the keywords that appear here are considered to be most relevant for the app. With that being said, the metadata in the title has the strongest effect/weight in the search algorithm.

The title can best be used for mentioning the brand, along with an indication of the app’s key function. For example, “Google Maps” uses their name/brand of the app followed by its functionality “Transit & Food”.

One key element to remember is that a great deal of keyword research and analysis goes into choosing the right words here.

Google Maps app page


An app subtitle is limited to 30 characters (including the spaces between words).

This section of metadata holds 2nd place in the hierarchy of effect on the search algorithm and is used to describe the app’s capabilities, features, elements, etc.

As you can see in the Google Maps example, “GPS, City Navigation & Traffic” covers the various capabilities and features of the app.

Keyword List

This section of the app’s store listing is used to target any keywords that are not mentioned in an app’s title or subtitle. The keyword list lies in the back-end of the store listing in the App Store Connect console, hidden from the world. Only the app developers have access to this list which is 100 characters long. To best utilize this space, extensive keyword research and tracking is needed in order to understand what to target.

Knowing what relevant keywords your app is ranking for and their search scores is crucial for optimizing your app.

It is important to understand that any redundancy in keywords between the title, subtitle and keyword list is a misuse of valuable space.

The ‘Given’ Keywords

In the App Store, there are some keywords that the search algorithm will automatically index your app for.

These are your app’s category names within the App Store that you have chosen to compete in. There is an option to choose two store categories – a primary category with two sub-categories, and a secondary category. An example of this may be a poker app that would choose Games as its primary category, with Casino and Card as the sub-categories, and Entertainment as the secondary category.

app category

Until now, we have discussed some elements of iOS metadata that effect the App Store search algorithm. It is important to remember that generating these elements of your app’s metadata should always involve an extensive keyword research followed by data analysis and tracking, so you can best optimize your app’s search visibility.

Later in the article, we will discuss the other elements of iOS metadata which may not affect the algorithm but can still play a part in providing information and driving conversion. These elements are the app’s description, promotional text and What’s New section.

Let’s elaborate on what affects the search algorithm and how to monitor change, with a look into keywords and some best practices.

What Affects the App Store Search Algorithm?

The App Store search algorithm is an ever-evolving element of the store and we can assure you it will continue to change. It is important to understand that one day, without any prior notice, the keywords that your app ranks for may change drastically. One tool that will help put your mind at ease is the AppTweak algorithm updates tracking tool. This is a free tool that monitors any dramatic changes in keyword rankings.

Apple’s App Store search algorithm indexes keywords both short-tail (single word search terms) and long-tail (search term phrases comprised of more than one word).

As we previously mentioned, there is a hierarchy which the algorithm follows when indexing keywords.

Another element of the algorithm is the mix & match of keywords from the title, subtitle and keyword list.

Looking back at the Google Maps example, one mix & match long-tail keyword may be “GPS Navigation”. As you may have noticed, “GPS” and “Navigation” do not appear next to each other in the metadata, and yet Apple has indexed Google Maps for this unique search term.

This behavior is not limited to the subtitle; long-tail keywords are combined by matching any words in an app’s title, subtitle and keyword list.

Google Maps app title

Other aspects may affect the algorithm, such as ratings and reviews – how is your star rating? Do you have quality reviews? Are you responding to negative reviews?

The App Store is more likely to promote good products – it identifies apps that have high ratings and good reviews and are engaging with their user base.

Metadata Best Practices

When optimizing your app for the iOS App Store, it is important to know that Apple – just like any other fruit – favors certain conditions. The App Store is a private store that holds the Apple name, which means that their interests are reflected in the store.

Here are some best practices to keep in mind for metadata (keep in mind that we always recommend reviewing the iOS guidelines):

  • Do not use any foul or vulgar language – Apple will reject any app updates if it finds or suspects any use of foul or vulgar language.
  • Do not use the word “free” – Apple does not allow apps to use this term in the app’s title or subtitle. You can still target this word in the keyword list if you choose to.
  • Avoid targeting competitors – We have seen Apple reject app updates in the past due to apps targeting their competition.
  • Avoid keyword stuffing – Redundancy of keywords in the areas that are indexed by the search algorithm is a misuse of valuable space. In the areas that are not indexed by the algorithm, keyword stuffing is irrelevant and may discourage potential users to download the app because it appears spammy.

Our final areas of interest for achieving greater search visibility are localization and Apple Search Ads.

App Localization

We recommend viewing this aspect both as an asset and as a tool for any app.

Localization is the art of delivering an app’s message in the various languages that iOS is open to.

For a full list of the countries an iOS app can localize for refer here.

Some things to keep in mind are:

  • Your app will have one listing as the primary listing. This listing will appear as the default for all countries that do not have a dedicated listing.
  • Some listings will be indexed for multiple countries. For example, there is an overlap between the English-US listing and the Spanish-Mexico listing. What this means is that any keywords that appear in Mexico’s listing will appear on a search made by a user in the US. This is a great way to broaden the reach of your organic search visibility.
  • Keyword research is a very important step here in order to understand what local keywords are relevant or not. A creative way of finding long-tail keywords for localized markets is using Google’s web search suggestions.

One example is the keyword “spielautomat”, which is “slot machine” in German. When you Google search the German keyword, the first suggestion in the auto-complete is “spielautomat kostenlos spielen”.

We recommend creating long-tail keyword combinations and uploading them to your keyword tracking tool in order to get a measure of search volume. You will also want to check their relevance by looking into the competition and see who ranks in top positions.

  • For more information on the significance of localization and what countries you should be localizing for, please feel free to contact our ASO experts.

Conversion Optimization:

In many marketing efforts, exposure (search visibility) is one step forward. The next step is converting potential users to download your app. In this next section, we will discuss some of the major aspects that influence conversion in the iOS ASO world. These aspects will include:

  • Graphics – each asset & tips
  • How to A/B test
  • Text structure
  • Ratings & reviews
  • Replying to reviews
  • Online preview tool

iOS Graphics:

In Apple’s App Store, the default graphic elements are the: icon, screenshots and videos. In this section, we will go over each element and give you some tips from our experience. In general, our take on store listing graphics is that they need to tell a story. It should communicate the value and experience that a potential user will get from the app.

Clash Royale is one app that has an interesting story told via graphics and here is our interpretation: The app icon can be viewed as a reflection of the app title – the expression of the character’s face depicting a king going into battle, reflecting the “Clash”.

Clash Royale icon

The next chapter in the story is the promotional video that’s live in the App Store. Beyond the standard gameplay, the video highlights specific features that correlate with the subsequent screenshots.

The video and the first two screenshots are what a potential user will see in the impression stage of the funnel. Clash Royale chose to highlight two gameplay features here: The first screenshot appears with a text caption of “Team Up with Friends” and the graphic showing gameplay of 2-Vs-2, and the second displays characters with the text caption “Unlock New Cards”.

Clash Royale screenshots

The next chapter in the story is the app’s listing page where the rest of the screenshots depict similar game features, which appeared in the promotional video as well, with captions reinforcing the graphics. These graphics come together to create a well-thought-out creative plan that reveals a story that is not only aimed at converting potential users to installers, but also at future user engagement and retention.

Looking at the thought process and vision involved in Clash Royale’s graphics, we can understand the value in delivering a message/story with graphics.

Let’s break down each element of the store listings: the icon, screenshots and video. You should take into consideration the difference between iPhone and iPad. The graphic assets for these two devices are different and should not be treated the same.

iOS Icon:

The app icon is one of the first visible elements of an app that potential users see, and has impact on conversion, brand and retention.

Remember that the app icon will stay with users on their phones.

From our A/B testing experience, we have found some trends that guide us while generating graphics for our clients. For the well-known brands, choosing an icon may be an easy choice because of branding decisions. However, we value data-driven decision making and recommend to always test variations of any graphic element. Sometimes a small change (i.e. the background color) of an icon may prove to raise conversion.

In the world of games, one leading trend that has shown positive impact on conversion is the use of a character’s face. We recommend highlighting a character, specifically the face, for A/B testing (given it is a relevant fit for the app). Below are some examples of mobile games that highlight a character or face.

app icons with characters

iOS Screenshots:

The app screenshots are a great tool to show the world what your app is all about. We understand from research on user behavior that the description is opened and read by less than 3% of users. Because of this, we aim to tell a story with the graphic assets instead of relying on the text.

Most apps combine text within the screenshots as they allow us to tell our story with more space than other graphic assets.

So what do people actually look at? Well, that’s is the million-dollar question.

In the past year, Apple has changed the number of screenshots that an app may upload to its listing. Currently, the maximum is ten screenshots for any app. However, utilizing all ten may not bring positive results.

From our experience, we have come to understand that the compositions should be very clean and self-explanatory.

The screenshots should reveal key elements of the product to potential users. Whether your product be a dating app, calendar or a card game, the message in the graphics should be setting an expectation of what the user will be receiving.

Below is an example of a well-known dating app with a look at the message their graphics deliver.

Tinder’s Screenshots:

Tinder screenshots

In these screenshots, we can see that there is less use of captions and more of a look into the app in use, showing the experience and value users may get from using the app. The screenshots implement brand colors and the app UI is shown inside an Apple device to help the user get a feel for what the app would look like on their phone.

We can see the value process that Tinder offers with their product right away, with the first screenshot’s short and to-the-point caption of “Match. Chat. Date.”

The first two screenshots tell a story: The first screenshot displays the distinctive “swipe right” feature with a ‘like’ stamp, giving meaning to the motion, and the profile image leads you to the next screenshot. The second screenshot continues the storyline by matching the users and showing the beginning of their chat. The third screenshots shows chats from previous matches as well as continuing Amanda’s story.

Screenshots 4 & 5 showcase other forms of exposure to fellow users of the app, and features including the ability to browse through a user’s pictures. Overall, these five screenshots reveal the app’s function from A-to-Z, along with different ways users can interact with the app.

iOS Video:

The App Preview Video is one graphic element that, in the eyes of Apple, is an optional add-on. But in our ASO expert eyes, the Preview Video is one asset that should not be overlooked. Apple allows for each app to have up to three videos as part of their product page. These videos appear at the beginning of the screenshot gallery.

As mentioned before, the story told by the Product Page is a key factor for achieving a high conversion rate. We recommend that the video takes into consideration what already exists and builds off that.

You should also be thinking about the layout of the graphics in the store. If an app has vertical (portrait) screenshots, the video should be in a vertical orientation. We have A/B tested combinations of mixing horizontal & vertical, and have seen more success with matching the video to the screenshots.

What the Users See:

Taking a look at an app with a vertical graphic display in the App Store, there are two stages that a user will see: The Impression view (left image below) and the Product Page view (right image below). In these two layouts, the video is the only dynamic element with an auto-play feature embedded in the store which starts playing the video once it is visible.

Clash Royale impression & product view

In the impression stage, on iOS 11 and later, there are three vertical elements shown, or one horizontal element.

A common combination of vertical graphic assets is one video in the first vertical slot and two screenshots in the remaining space.

A/B testing the impression stage is a crucial part of ASO, which optimizes the upper funnel of user acquisition and, in effect, drives more organic installs.

Creative Sets Testing

Since Apple doesn’t allow you to directly A/B test on the App Store, one way of A/B testing the impression view is a feature of Apple Search Ads called Creative Sets Testing – a paid marketing activity that helps drive direct insights for organic traffic (more efficiently than the App Store Connect console).

With Creative Sets Testing, an app marketer can choose to group varying graphic assets to present in the impression stage. However, as with everything, there are limitations. Apple limits the graphic assets an app can choose from for Creative Sets Testing to the graphic assets that are currently live in the store.

If you are considering testing 1-of-2 preview videos, they both must be live in the store for you to run Creative Sets Testing on which preforms better in the impression stage. For more information on Apple Search Ads and how to best run creative sets, you can contact our ASO team.

In the Product Page view, a Preview Video will appear in the beginning of the screenshot gallery. If users have not already seen the app’s video, they will have second chance to do so at the Product Page view stage. For this phase of the funnel, there is no option for A/B testing with creative sets like in the Impression phase.

Text Structure:

The message that the app delivers in the App Store is a big part of what will influence the conversion rate. In the app store, there are various segments of text that appear in the Product Page that can be crafted in a way to aim at engaging the users and work at raising conversion rates.

Over the past few iOS updates, the order of the metadata has changed, so be sure to check your data and see what devices and update versions are a major part of your target audience. It is also important to know that users who have downloaded your app in the past may be repeat installers who see the store differently than first-time installers.

The various elements of text in the product page are the Title & Subtitle, which we have already covered. The Title and Subtitle are the first sections of text that a user will see and use to understand if the app is right for them. The next sections are What’s New, Promotional Text and Description, which can be written in a way that encourages users to download an app.

What’s New

The What’s New section of an app has seen some changes with Apple’s latest iOS update. For first-time installers, this area of text has been given a spotlight by getting placement below the Reviews & Rating scores. For users who have installed the given app and then uninstalled, the What’s New section will appear at the top of the app’s Product Page.

This unique characteristic makes drafting the message here even more interesting.

The message is primarily for communicating the reason for an update, such as bug fixes or any new features added to the app.

One example of a What’s New section that is aimed at engagement is Evernote, whom have chosen to highlight the fact that they have listened to the requests of their existing users.

Evernote has added a new template feature to the app which has made the UX a smoother experience for users. You can also see that Evernote has snuck in another feature ‘Dark Mode’ which users may prefer to use. Understanding user behavior is important for conversion optimization because it will not only help raise the number of downloads, but may also positively affect retention.

Evernote What's New section

Below are some more creative uses of the What’s New content that are funny, informative and engaging.

Hulu What's New section(Credit: StoreMaven)

Candy Crush What's New section(Credit: StoreMaven)

Promotional Text

This is a section of text that will appear at the top of the description and is limited to 170 characters. The promotional text is not indexed by the algorithm, so no need to worry about what keywords appear here.

This text is normally used for conversion optimization and conveys any ongoing or short-term product features.

What makes this area special is that, while any metadata changes need to be made via an app update, the promotional text can be modified at any time. So, if you updated your app listing before Christmas and you would like to convey a message dedicated to New Year’s right after, the promotional text may be a good fit.


This area of the product page may not have any impact on the search algorithm, yet is still a value-adding element of any store listing. The app description can be up to 4,000 characters long and should provide users with information about the app. You want to make sure you’re providing the right content for your user base.

One key factor here is the 2-fold appearance of the long description. On any app’s product page, only the first 3 lines (about 133 characters) of your app’s description will appear, which is often referred to as ‘above the fold’. At the end of the 3 lines, a ‘Read more’ button will appear which will reveal the rest of the description.

In a study conducted by StoreMaven, we know that only 2% of users who visit an app’s product page open the full description. With that in mind, you want to make those first 3 lines deliver a message that will be the deciding factor for users to install.

Structuring the beginning of the description to show key factors relating to the app is one more step towards delivering the right message to a potential user and working at conversion optimization.

Ratings & Reviews

Ratings and reviews play a part in both conversion and search visibility. In this section, we will go over the placement of the rating score & reviews in the store, and some tips about both.

First of all, let’s define what ratings and reviews are. A rating is a score – out of 5 – that users will attribute to an app. This rating score is standard in the App Store and is used for all apps. Reviews are similar to ratings in that users provide a score for the given app, and also leave written comments regarding the app.

The standard for any app’s rating score is the average of all ratings and reviews together. This rating score is presented in both the impression stage and the Product Page view at the top, underneath the app icon without any reviews. The full ratings & reviews section of the app is placed below the app description, highlighting the rating score, the distribution of rating (according to their relevant 1-5 score), followed by a mix of highlighted reviews.

Monitoring Reviews

One tool that we find useful to monitor ratings and reviews of apps is App Annie. App Annie visualizes the data on ratings and reviews in a way that allows for better tracking and reporting. The section on rating and reviews is a part of their free version, and anyone can register to use this tool.

From an ASO view point, ratings and reviews are a source of data that is collected from users. Mining through the app’s reviews may reveal what features of the app users like and dislike. This is important for both marketing and product. We have had success in the past from understanding what users like most, and by showcasing that in the message delivered in the product page. This is a regular process that is part of how we optimize conversion rates for apps.

Prompting for Reviews

For apps that have few reviews or that want to improve their rating score, prompting for reviews is an option.

Prompting for reviews from within the app is one way to help boost an app’s review score.

It is best to build a strategy that will take into consideration the most opportune moment to prompt users. Sometimes efforts to increase the rating score via prompting can backfire and hurt both the app’s rating score and user retention.

Replying to Reviews

Replying to users who have taken the time to share their experience and insights can also prove to be beneficial. There is an option to reply to individual reviews through the App Store Connect console.

It is considered ‘best practice’ to reply to reviews and engage users through this channel of communication.

Some developers choose to reply to negative reviews, yet we recommend to our partners to reply to all reviews – good, bad and those in the middle.

Optimizing Store Presence & Exposure:

In addition to users searching for apps in the App Store, users are also exposed to a variety of apps through browsing the App Store’s different content. Understanding how the App Store functions can lead to higher Browse exposure, which can benefit an app greatly.

In most cases, the amount of store visibility an app gets for Browse surpasses the amount of unique keyword searches. However, when comparing conversion levels for the two sources of organic traffic, Browse does not convert as well. Understanding how to raise the Browse conversion rate can lead to raising organic installs significantly.
Getting featured in the App Store is one way to get more Browse visibility, which can translate to organic installs.

Install spikes in iOS have been known to reach 800% increases as a result of getting featured. The App Store has evolved a number of times over the years and new ways for an app to get discovered have been added to the store. Some of those being:

  • The Today section
  • Game of the Day
  • App of the Day
  • Now Trending
  • Our Favorites
  • The Basics
  • The Daily List
  • Let’s Play
  • Life Hack
  • Try Something New
  • Gaming 101
  • App Culture
  • Meet the Developer
  • Get Competitive
  • Featured Game
  • Featured App

As you can see, the App Store has a wide variety of options for apps to be visible in ways that are not unique searches. Getting featured, though, is not achieved easily.

To raise your app’s chances of getting featured, know that the App Store favors apps that have the following bases covered:

  • Little to no bugs in the product
  • Frequent app updates
  • Localized listings
  • Frequent replies to reviews (good and bad)
  • A mention in the form that the app is only live in the App Store, if relevant
  • Quality keywords in the metadata
  • Quality graphics
  • Use of Apples APIs

If you think that what we have mentioned reflects your app, then you have one more step to go – APPLY! To get featured, you must reach out to Apple yourself and explain why they should feature your app.

One tool that we use to track apps that have been featured is AppFollow, which provides insights and tracking on featured apps. Now that iOS provides breakdowns of organic traffic from keyword searches and Browse, it is easier to follow the effects of a feature by checking the Browse KPIs. Follow through and track the quality of the users, the effects on conversion rates, and other metrics to gain important insights on how the extra visibility can be more productive in the future.

Promoting In-App Purchases

Another way to further optimize your store presence is by promoting your in-app purchases. In the App Store, users are already exposed to the various in-app offerings and can choose to buy them before the app is even downloaded to their phone.

Today, iOS allows apps to promote up to 20 in-apps purchases on their product page. Apple has even come out with an API for customizing promoted in-app purchases to allow app developers to further optimize monetization.

It is important to remember that Apple has an interest in apps making money, and apps that follow the guidelines and best practices will get more exposure and potential to generate more revenues.

Tracking & Monitoring:

We need to be able to track our efforts in a way that allows us to quantify our success in order to understand the significance of any activity. App Store Connect is the default platform that provides data on an app’s performance.

The platform is not perfect and working with the data in iTunes has its limitations. Below is a list of some of the limitations:

  1. Updating – no ease of updating like in Google Play
  2. Filtering data – it is only possible to filter by two parameters in the Analytics section
  3. No keyword data – Apple does not share any organic search data on keywords
  4. Not the full data – the data provided only reflects users who choose to opt in
  5. No benchmarks – there are no benchmarks for CVR or crashes
  6. No app comparison – for developers who have multiple apps, there is no way to compare apps

At yellowHEAD, we have solved some of these issues by developing our own dashboard that we use to track performance and KPIs. We solved the issues of filtering data, benchmarks and app comparisons with our in-house data visualization platform. For more information, feel free to contact our ASO team.

Alison data visualization

Understanding the Limitations:

Let’s elaborate on what can be done with the data that Apple does show.

Traffic Sources

When using App Store Connect App Analytics, it’s important to differentiate between the sources of the incoming traffic. Whether it be Impressions, Product Page Views or App Units (Installs), it’s crucial to understand the source of the traffic in order to reach actionable insights.

Under Metrics, we recommend filtering by Source Type to see the significance of the organic traffic compared to paid traffic.

For organic traffic, sum up App Store Search and App Store Browse, and for paid traffic, sum up App Referrer, Web Referrer* and Unavailable (*some Web Referrer traffic may come from organic web assets). You can also filter for more in-depth data on traffic from different Regions (countries) to report on your localized listings’ ASO progress.

Keyword Rankings

You should also understand that the analytics from App Store Connect is just one part of the organic funnel. Another main area to track is keyword rankings. We target and retarget keywords frequently and are always hungry for results. Using a keyword tracking tool is a must, and when reviewing the data, a lot of volatility may appear in rankings.

We recommend averaging keyword rankings from an entire week to get a better picture of how much visibility was gained – looking at specific days is not the most accurate measure.


Unfortunately, benchmarks are not shared by Apple, yet we understand the importance of knowing how well an app is preforming. Conversion benchmarks are provided in the Google Play Console, and for iOS, AppFollow has compiled a large amount of data that shows conversion in various industries for several localities.

App Update Rejections

Last but not least, we feel that we should elaborate on the issue of app update rejections. Apple reviews apps before a new build is uploaded to the store. Apps that do not follow the guidelines and violate Apple’s principles will receive a rejection notice. It is important to understand that this is not the end of the world; it just means that there is more extensive work to be done.

When an app receives an update rejection, the current version will stay live and not be affected.

You will want to pinpoint the reason for the rejection and make the necessary changes that Apple requires.

Some reasons that may lead to app rejections are:

  • Use of profanity and foul language in the metadata
  • Screenshots not showing gameplay in the first screenshot and throughout
  • Use of the keyword “free” in the product page metadata
  • Binary screenshots – using the same screenshots for iOS and Google Play
  • Metadata providing access to external mechanisms for purchases

To Conclude:

Understand that Apple controls the App Store and that the App Store reflects Apple. ASO is an ever-changing process due to the fact that the App Store is always evolving.

If you choose to put this article to use, we feel that your ASO efforts in the App Store will be off to a great start.

One thing to always remember is that your app’s Product Page needs to reflect the value that users are looking for. Understanding the needs of users is the key to great ASO.

If you have any questions or need more info about ASO services, feel free to reach out to us.

Check out more of our ASO expert tips.

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