What is the Keyword Field?
The keyword field is a metadata element on the product page of every iOS app. It is invisible to users. So it does not matter for conversion rate optimization. But as it is one of the four indexed metadata elements, it can create visibility in search results. Apple’s search algorithm will find keywords in this metadata element and rank an app for them.
The weight of the field regarding the search algorithm is lower than the weight of the app title or the subtitle, but higher than the weight of the titles of in-app purchases. That means that apps with a keyword in the keyword field, in general, cannot outrank an app with the same term in the app title or subtitle.
Apple’s algorithm will rank an app for long-tail keywords that consist of multiple single terms. This is true for combinations of two words in the keyword field. But it is also valid if one term is in the keyword field and the others are in the title or subtitle. In contrast, the algorithm does not index combinations with words in IAP titles.
App owners can insert up to 100 characters. That equals about 10 to 20 keywords, depending on their length. Commas should separate all terms in this field. See the example below for reference.
Like the other indexed metadata elements, app owners can manipulate the keyword field only when a new app version is pending release. For live versions, it is not possible. That means that adjustments to the keyword sets should be planned before a new app version is uploaded to iTunes Connect.
One Field per Localization
The keyword field is language-specific. So for every localization, app owners need to create a new keyword set to fill the field. According to Apple’s guidelines, the language of terms in the field should match the localization. So for Italian, the keywords should actually be Italian terms. However, in reality, Apple’s reviewers do not enforce this rule consistently. Therefore, it depends on the goodwill of the reviewer whether terms in a language that does not match the localization are accepted or not.