A Complete Guide to App Store Optimisation (ASO)


19th July 2019


13 min


Bethan Vincent

You’ve come up with an amazing idea‚ validated your business model‚ had your mobile app developed and tested. The big question now is – how do you get it in front of users.

This guide will help you understand the mechanics that makeup App Store Optimisation (ASO) and some of the techniques you can use to ensure your app gets in front of an interested audience.

What is ASO?

ASO is the process of optimising mobile apps to rank higher in an app store’s search results. The higher your app ranks‚ the more discoverable it will be by potential customers and therefore the more likely it is to be downloaded. 

It’s important to note that app discovery doesn’t just happen in the app store‚ but over 40% of users do use the app store to search for apps

Other discovery channels include:

  • Word of mouth 
  • Online reviews and articles
  • Online and offline advertising
  • Search engines
  • Social network mentions and shares
  • Browsing top app charts 
  • In-app store advertising 

Understanding Search and Rankings

Much like Search Engine Optimisation‚ the goal of ASO is to ensure your app appears at the top of the organic search results for keywords related to your app. 

As we will come onto below‚ keywords aren’t the only ranking factor that determines search results‚ however they are certainly the most important. 

Types of keyword

Branded: Users will have prior knowledge of the product and/or brand and will use specific branded keywords‚ e.g. “Spotify” or “Bumble”

Categorical: Users will be looking for an app that fits into a distinct category‚ e.g. “free games for children under 10” or “productivity apps”

Needs based: Users will be looking for a solution for a distinct problem‚ e.g. “sleep aid” or “help with weight loss”

Keyword Research

Before you start optimising the ranking factors below‚ it’s important to spend a significant amount of time identifying the keywords you want to rank for. You need to know which keywords are most relevant and frequently used by your target audience.

These keywords will be a mixture of the keyword types listed above‚ however if your app or brand is new to market‚ branded search volume will be naturally lower as fewer people will have heard of you.

Start off by defining your audience – think about demographics and also what are their pain points‚ goals and biggest challenges? This will give you an insight into their needs and why they might be searching for your app as a solution. Think about the search queries they might use to solve their problem and note them down.

When you’ve created this list of initial search queries‚ put those into the app store search bar and look at the autocomplete suggestions. This will give you an idea of similar search queries to add to your list. 

You can then further build up your list by looking at your competitor’s keyword usage. You can also have a look at search behaviour on the wider web using tools like Google Keyword Planner or Google Trends

The aim at this stage is to find as many keywords as possible that are related to your app‚ so don’t worry if your list is in double or even triple digits.

Determining The Right Keywords

By now you should have a reasonably large list of keyword ideas‚ but you can’t optimise for them all. At this stage you should start pruning your keywords to end up with the tight selection that you will then optimizing for.


Keyword relevancy is undoubtedly the most important factor‚ especially because conversion rate is also a ranking factor (as discussed below).

Simply put‚ if you’re optimising for keywords that don’t really fit your app’s purpose‚ users searching using that keyword will be presented with a solution that doesn’t fit their needs. They are therefore much less likely to download your app. This subsequently impacts your overall conversion rate. 

Go through your list and remove any keywords that you believe are not relevant to your app.

Ask yourself – if someone searched using this query‚ would they download my app as a solution or a good fit?


You ideally want to aim to rank in the top 10 for any keywords you are optimising for. 

Much like only 10% of people look at the second page of Google results‚ users are much less likely to look below the top 10 app store results.

This means that there is a balancing act to play between trying to rank for popular high competition keywords‚ which usually have higher search volume but are harder to rank for. Then ranking for easier less competitive keywords which have lower search volume. 

If you have been involved in SEO‚ you may have come across long-tail keywords‚ which are usually three or four very specific phrases‚ e.g. “fitness tracker for pregnant women” as opposed to “fitness tracker” – these long-tail keywords are usually lower competition‚ however‚ they must pass the test of relevancy. 

Many experts in the field believe that higher rankings on less popular keywords are more useful than lower rankings on popular keywords. Being below the magic top 10 results means that users are much less likely to find you regardless of whether the keyword is popular or not.

Tip: Use ASO Keyword Optimisation tools to research keyword competitiveness and monitor over time

Search Volume

At this stage you may have removed some high competition keywords depending on your findings. You can always add those back in later as your app becomes more popular (especially if you can combine them with branded terms).

You now need to look at look at the remaining keywords’ popularity to make your final selection. If you have keywords that are semantically related (similar in meaning)‚ or synonyms‚ you ideally want to pick the option that has the highest search volume‚ as that gives you the opportunity to get in front of as many people as possible.

Tip: Again‚ you can use ASO Keyword Optimisation tools to research search volume. 

How many keywords should you try and rank for?

There’s no hard and fast rule here‚ you should ideally have a core set of three or four keywords that are highly relevant to your app‚ low-ish competition and have the highest search volume when compared with similar terms.

You could also start off with high competition terms to see whether you can obtain a good rank. For the keywords on which the app won’t rank‚ you can shift gradually to longer-tail and lower competition terms until you get a decent rank. This requires a significant amount of monitoring and testing‚ so you need to ensure you have a system in place to monitor and review the process. 

Ranking factors for App Store and Google Play

Once you have your keyword list‚ you need to now need to ensure your keywords are well placed in the various ranking factors and also optimise for secondary ranking factors. 

Neither Google Play nor the Apple App Store disclose their ranking algorithms publicly‚ so we can not be sure exactly which factors influence rankings and in what proportion.

However‚ this is a list of factors many people believe to have an effect on the app store rankings‚ along with their perceived importance. 

Keywords and Metadata

  • Title/App Name (30 characters long for iOS‚ and 50 characters long for Android.)

Title is the first and one of the most important keyword factors‚ because it has an effect on both search results and conversion rate to install. Try to include your brand name and a key set of keywords which also give the user an understanding of the apps functionality and use‚ e.g. 

Spotify – Music and Podcasts

Bumble – Meet New People

  • Short Description (Google Play – 50 characters)

On Google Play you can include up to 80 characters in the short description field. Use this to provide a clear description of your app‚ including some of your main keywords that you want your app to rank for.

  • Subtitle (App Store -30 characters)

On the App Store your app’s subtitle appears below your app name throughout on iOS 11 and the Mac App Store on macOS Mojave and later. A subtitle can be up to 30 characters long and should include main keywords and a clear app description.

  • Description (4‚000 characters. Note that users only see first 5 lines unless they click more‚ around 200 characters)

Your description should provide a concise‚ informative overview of the app followed by a short list of main features. The first few sentences of your description are the most important and should include your main keywords. This is especially important for Google Play‚ as this is one of the main places where Google finds the keywords to index your app.

  • Promotional Text (App Store – 170 characters)

Promotional text is a 170 long field that appears at the top of the description Consider using promotional text to share the latest news about your app‚ such as upcoming features or content.

  • Keywords Field (App Store – 100 characters)

The App Store allows you to input keywords in a specific field. The keywords are limited to 100 characters total an improper use of keywords can result in your app being rejected from the App Store‚ so don’t be tempted to stuff in those irrelevant keywords we discarded earlier on!

  • URL (Google Play)

Similar to Google search‚ keywords included in the URL string act as a strong ranking factor on the Google Play store. Once your URL is set it can not be changed‚ so take your time in considering which keywords to use. 

Secondary Ranking Factors

Please note‚ these secondary ranking factors do differ between Google play and the App Store as indicated in the table at the bottom of this page.

Category selection

Choosing where you get listed is an extremely important and you need to choose consciously. Sometimes your app will clearly fit a very narrow category‚ in other instances you may be looking at selecting from a couple of categories. 

This is another area where it’s worth looking for low competition opportunities. Entertainment‚ for example‚ is heavily dominated by the likes of Netflix and established media companies which makes it harder to rank in. Look at leaderboards to understand the competitiveness of each category. 

Relevance is also a key consideration too‚ you do not want your app to be listed in a category where it will feel out of place‚ as your conversion rate will be lower. Apps found to be miscategorised can also be rejected from both Google Play and the App Store. 

Number of Downloads (Conversion Rate)

There appears to be a positive correlation between the number of downloads and app store rankings‚ which seems fairly self evident. This has implications for people targeting competitive keywords‚ as you need a significantly larger number of downloads to rank highly.

Ratings and Reviews

Apps with higher ratings and more user reviews will be ranked higher on both app stores. This has a few consequences‚ firstly you need to ensure your in-app experience is worthy of a five star review. You may also want to consider your strategy for encouraging users to leave positive reviews. 

App updates

Both Apple App Store and Google Play consider the frequency of updates as a signifier of app quality. 

Apps that are frequently updated also generally attract more reviews and positive ratings‚ which will help further improve your rankings. 

User Retention and Engagement

Uninstalls impact rankings specifically in the Google Play store. The reason for this is that Google wants to prevent app users from being unnecessarily frustrated by poor app experiences. 

This means you must focus on delivering a seamless user experience‚ alongside providing a compelling reason for users to keep your app on their device.


Localisation improves your search visibility as it makes your app available to users searching in specific languages. Users will generally perceive apps presented in their own language as more relevant and trustworthy. 

Consider taking your existing metadata and translating it into different languages to enable you to reach an international audience. 

Backlinks and Listing Visits

It is widely believed that both Google and Apple factor in your app’s total page visits and product page backlinks when determining your search and overall ranks.

Simply put‚ the more traffic you drive to your listing‚ the higher it will rank in search results. Use your main website and social media channels to help give your traffic a boost.

Developer History (Google Play)

Google favors apps from a developer with a positive history and ranks them higher in search. This is another reason to focus on app quality before launch and also ensure you work with a highly-regarded developer who has released a number of apps.

Download Velocity (Google Play)

It is believed that the volume and velocity of downloads after an app is launched or updated do have an impact on rankings in the Google Play store. This means that you ideally want to drive the most downloads in the least amount of time.

This can be done through correctly optimising for high volume keywords and driving additional traffic to your listing. You may also want to consider running a short in-app store advertising campaign. 

Hidden Factors in App Ranking

Much like traditional SEO‚ the ranking algorithms for both the App Store and Google Play are not publically available‚ however people have been able to interpret the ranking factors above through logical investigation and experimentation. This means that there will always be unknown factors at play which will determine your app’s performance. 

It is also worth noting that the Google Play algorithm is generally considered to be more complex than the App Store’s. 

Tip: The best way to continue optimising performance is through sustained experiementation and testing.

Secondary App Ranking Factors by Platform


Google Play 

iOS App Store

Keyword Use



Number of Downloads



Ratings and Reviews



Update Frequency



User Retention


Backlinks from Web



Download Velocity


Developer History


Hidden Factors



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