The App Store keyword field: limit, rules and examples

Apple’s search and product page guides say keywords are “limited to 100 characters total” (Apple: search, product page). The App Store Connect help describes the same field as up to 100 bytes (Apple: platform version information).

For plain English the two are the same: one letter is one byte. They differ for other scripts. In UTF-8, letters like ä or é take two bytes, and Japanese, Chinese, Korean or Thai characters take three. A Japanese keyword field can therefore hold far fewer than 100 characters. The keyword field checker shows both counts.

Separate terms with commas and no spaces. Spaces are fine inside a phrase. Apple’s own example is Property,House,Real Estate (Apple). The App Store Connect help adds that each keyword should be longer than two characters (Apple).

A space after every comma looks tidy and costs you one character per keyword. With 15 keywords that is 15 characters, enough for two more words.

Apple is explicit about what not to put in the field (Apple: search, App Store Connect help):

• Words that are already in your app name, subtitle or category. Your app is already searchable by its name and your company name.
• Plurals of words you already have. Apple’s example: “climbs” and “climb” count as duplicates.
• Generic terms such as “app” or “game”, and filler words such as “the” or “to”.
• Special characters such as # or @, unless they are part of your brand.

Names of other apps or companies, trademarked terms you are not allowed to use, celebrity names, and words that have nothing to do with your app. Apple calls improper keyword use a common reason for App Store rejections (Apple), and the App Review Guidelines ask you not to pack metadata with trademarked terms or popular app names (App Review Guidelines 2.3). Competitor names are not a shortcut.

Apple allows both. It does not document whether words from different fields are combined into longer phrases. Many ASO practitioners observe that they are, so they write single words (spanish,lessons) instead of full phrases (spanish lessons) to fit more terms. If a phrase only makes sense in a fixed order, keeping it together is the safer choice. Check your rank after the release to see what works for your app.

A made-up example. App name Lingua: Learn Languages, subtitle Spanish, French & German. The first keyword field:

language learning, learn spanish, learn french, best language app, Duolingo, vocabulary, grammar

What is wrong with it:

• A space after every comma (6 characters wasted).
• “learn”, “spanish” and “french” are already in the name or subtitle.
• “language” is the singular of “languages” in the name, a duplicate by Apple’s rule.
• “app” is a generic term, and “Duolingo” is another company’s app name: a rejection risk.

italian,japanese,korean,chinese,vocabulary,grammar,flashcards,lessons,speak,practice,english,phrases

Exactly 100 characters, no repeats, and every word is a new chance to be found: the app now also covers “learn italian”, “japanese lessons”, “korean flashcards” and dozens of other combinations, if the words are combined as described above.

Keywords are set per localization (Apple). Each language you add gives you another 100 to fill, and some of those localizations are searchable in several countries. See App Store localization for keywords.

Paste your name, subtitle and keywords into the free App Store keyword field checker. It runs in your browser, counts characters and bytes, and flags spaces, repeats, plurals and generic words. LocalASO’s Optimize tab does the same for every language and also proposes the words to add.