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App Store Optimization (ASO): Selecting the Right Keywords (Part 2)
by Szilard Szasz-Toth on 07/07/14 07:27:00 am   Featured Blogs

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The following blog post, unless otherwise noted, was written by a member of Gamasutra’s community.
The thoughts and opinions expressed are those of the writer and not Gamasutra or its parent company.


In the first part of this series we have described how to find relevant keywords for your app and target audience. You should have a pool of potential keyword candidates and their corresponding keyword properties (traffic and difficulty). Now it's time to start with the actual selection process. To get you started (and not scared off), this post presents an easy-to-follow and hands-on guide on creating a solid keyword list. All the hard preparation work will now pay off!

2. Select your keywords wisely

The Apple App Store limits the total length of your keyword list to 100 characters (separated by commas). It is therefore very important to decide which keywords to include and which to drop out. Our ultimate goal is to select those keywords from our keyword pool that will most likely lead to actual downloads of our app. The ideal outcome for each keyword would equate to:

(High Relevance) + (Appropriate Difficulty) + (Some Traffic) = Increased Downloads

We have already identified highly relevant keywords, so the remaining pieces of the equation revolve around difficulty and traffic.

  • Appropriate Difficulty: We need to target keywords that are not too difficult to rank for, otherwise we have basically no visibility in search rankings. Remember, we are not Angry Birds (yet)!
  • Some Traffic: We need keywords that have some search volume, otherwise we have wasted precious space in our keyword list. No volume equals no downloads.

We generally have two options at this stage, either select our keywords by traffic or by difficulty. So which keywords should we choose? The intuitive answer may be to select the keywords with the highest traffic numbers. For a math game it may therefore seem obvious to include the keyword “game”, which has the following characteristics:figure07

As you can see the keyword has a very high search volume, but also a tough difficulty value. You may be inclined to think that high traffic keywords are a good target. If your app ends up getting only a fraction of that high traffic, you should already see some good download figures (e.g. if you get 1% of the traffic of 100,000 search queries per day, assuming a 10% conversion rate, you end up with 100 downloads for that key). But a keyword with such characteristics (high traffic, high difficulty) will put you into direct competition to all the Angry Birds in the app store.

If your app is new to the market and you have no real exposure yet, it is very unlikely that a difficult keyword will lead to any downloads at all. The more difficult a keyword is, the harder it will be for your app to rank in the top spots. Who will have the patience to scroll down to rank #661 to discover your app in the search results? You should generally try to appear on the first or second page of the search results. Ranking outside of the Top 10 for a keyword will already decrease your chances of being discovered and downloaded considerably! Instead of focusing on keyword traffic, it is therefore much more important to focus on keyword difficulty (i.e. traffic is secondary to difficulty).

2.1 Select your keywords by difficulty

Assuming that this is your first game and you have no real exposure, you should consider using keywords with the lowest difficulty scores (all keywords in your current list should be relevant to your app and have a traffic > 0 by now). So go ahead and sort your keywords by their difficulty scores (from easiest to hardest) and then select the ones with the lowest values, i.e. easiest to rank for.

Note that your actual ranking for a specific keyword will depend on many different factors and not only on its difficulty (which is just a theoretical value calculated by your ASO tool based on some assumptions of the app store ranking algorithm). So a low difficulty score will not automatically guarantee a high ranking. The app store ranking algorithm is essentially a black box and some or all of the following factors may influence your resulting ranking:

  • Number of total downloads (current version/ previous versions)
  • Download momentum (acceleration/ decceleration of download rate)
  • Number of Reviews (positive vs. negative, current/previous)
  • App usage/ user engagement (how often and how long is your app used)
  • Discard rate (how often and how quickly is your app deleted)
  • Click/ Download rate (how often is your app clicked/ downloaded in the search results)
  • etc.

As a general rule of thumb you want to rank in the top 10 for all of your keywords (that have traffic). This requires a lot of testing and re-evaluation, so don’t expect to achieve top ranks in your first app submission for all of your keywords (we didn’t). ASO takes time, requires continuous monitoring, regular adjustments and is an evolving process. Additionally, app store providers change their algorithm from time to time, so it is important to react on changes and stay on top. Choosing highly relevant, low difficulty keywords that have at least some search volume is your best initial guess. With each app iteration and evaluation of your keyword list, you will get a better picture of your target difficulty values. So don't give up after your first submission and keep testing!

2.2 Difficulty Brackets

If your app is already up and running, you should analyse the rankings of your current keyword list. Ideally, you will start monitoring the values over time. This information is very valuable and will help you in your decision process. Knowing your keyword rankings (in combination with other determinants like downloads, ratings, etc.) will help you target the right difficulty range in your next release.

Let's look at the following sample values:Screen Shot 2014-06-27 at 20.50.56

You can immediately see that this app is ranking poorly on many of the selected keywords, but ranks in the top 10 for a few others. As you might have guessed, this list needs some serious optimization, but the stats will help you make the right choices for your next update. We therefore determine difficulty brackets to see which keywords we want to target. The current rankings and difficulties are our best estimate of future rankings.

By looking at the sample values we have identified the following difficulty brackets:

  • Target Difficulty [Difficulty <= 2 and Rank <= 10]: These are your top picks. You have a realistic chance to score in the top 10 for similarly difficult keywords.
  • Intermediate Difficulty [2 < Difficulty <= 4 and 10 < Rank <= 30]: This is your extension list. If you cannot identify enough keywords with a target difficulty, you can fill up your list with these keys.
  • Out-Of-Your-League Difficulty [Difficulty > 4 and Rank > 30]:This will be your exclusion list. You probably have no chance to rank anywhere near the top charts, so forget about targeting these for now.

You should try to exclusively select keywords from the target bracket and disregard all other keys. In case you should not have enough keywords with a target value, you have two choices:

  1. You can extend your pool to include keys from the intermediate bracket. This is the faster approach, but will lower the overall quality of your keywords list (as the average estimated ranking will decrease).
  2. You can keep searching for more relevant keywords that have a target difficulty value (which means going back to Part 1). This will ensure a high quality, but will will take much more time.

In general, you should never include keywords that are out-of-your-league in your keyword list. You could, however, include very important, highly difficult keywords in your app title (we decided to include "math" in our title, for example). Keep in mind that this will be a trade-off between brand recognition and ASO. So try to avoid including too many keys in your title.

In addition to analyzing ranking, difficulty and traffic of your current keywords, you could also look at download numbers, ratings, etc. to better understand under which circumstances your app has achieved these rankings (as mentioned earlier, other factors will also influence your ranking).

As a good practice going forward, you should start to track your keyword rankings as soon as your app has been accepted. This will allow you to determine the average difficulty value needed to catapult you into the top charts. As your reviews, downloads, rankings, etc. will change over time, so will your keyword rankings and the difficulty brackets. It is therefore important to constantly re-evaluate your keyword list. Otherwise you may miss some key opportunities.

2.3 Traffic is king

So far we did not pay much attention to the traffic value and have focused on difficulty. Traffic is without a doubt very important (no traffic = no downloads). But as long as your app is flying under the radar, the difficulty value is much more important. The traffic value is particularly useful, if you have to decide between similarly difficult, but competing keywords (more potential candidates than slots). In case you have to choose between multiple keywords with pretty much the same characteristics (similar difficulty, keyword length, relevance, etc.), traffic will be king.

Let's say you have only one more available spot in your keyword list, but three potential keywords to choose from. All three keywords will fit into your list. They are highly relevant to your app, have identical difficulty scores, but different traffic values. In such cases, you should always choose the keyword with the highest traffic, because that keyword will most likely generate more downloads. But always remember, traffic is secondary to difficulty (except if you are super successful and can target the most difficult keys anyways). So before looking at the traffic value, make sure to only select keywords that will potentially rank you in the top ten!

3. Further considerations

  • Space is precious (Apple limits your keylist to 100 chars, including delimiters). So never use unnecessary whitespaces!
  • Only include singular and plural of a word, if both keys have very similar and have desirable characteristics!
  • Words in the app title are recognized as keywords, so think about including some difficult must-have keys in the title (e.g. math). But don't spam your title, if you want to build a brand name!
  • Keyword combinations count as well. Good combos will improve the quality of your list. Some words may be combined with many other keys and add up to your overall keylist quality ( e.g. "practice" can be combined to "math practice", "multiplication practice", "geometry practice", etc.)!
  • The Apple App Store ranking algorithm does (most likely) not take keywords from your app description into consideration!
  • Keyword length is important, because people are lazy. Try to stay below 10 chars per key (who will type in "bestmathgameevermadeonthisplanet"?)!
  • Iterate quickly. Each update will give you a new chance to drop out under-performing keywords and add in fresh ones!

Wrapping it up

In this part of the series we have described how to select your keywords in an easy to follow way. This guide should get you started and hopefully boost your download numbers. Keyword optimization is not magic, but it requires continuous work. With each iteration of your app you should get a better feel for which keywords to target. ASO takes time, so stay on top of it!

So far our iterative selection process looks like this:

  1. Create a pool of relevant keywords
  2. Get difficulty and traffic values
  3. Select by difficulty
  4. Optimize traffic

In the next part of this series we will take this simple approach a step further and introduce our multi-factor scoring model. So don't stop now, if you are looking for the ultimate keyword list!

Do you have any questions, feedback or ideas? Let us know in the comments!

The original blog post appeared on our dev blog:

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