How to fill the App Store keyword field: the rules Apple states and the ones it doesn't

Apple gives you 100 bytes in App Store Connect: commas, no spaces after them, no plurals of words you already used, no category names, no competitor names. The rest of what matters is not written down anywhere. We measured one of our apps across 27 storefronts and found that a storefront's search reads more than one of your localizations, which changes how much room you really have. Pack the field with our keyword field packer.

The short version

Five rules cover most of it: one phrase in the name or subtitle, single words in the keyword field, no word repeated anywhere the same storefront reads, no competitor names, and demand checked before you spend bytes. Everything after this section is the evidence — Apple's own pages first, then what we measured on one of our apps.

• Put your one most important phrase in the app name or subtitle. The keyword field holds single words that combine with it.
• Write single words separated by commas with no spaces: goals,reminder,planner. Spaces are only for words inside one phrase.
• Never repeat a word. Not across the name, subtitle and keyword field of one localization, and not across two localizations the same storefront reads.
• Leave out plurals, category names, the word "app", special characters, competitor names and trademarks.
• Check that a word has demand before it costs you bytes.

What Apple writes down

Apple states the field's limit, the format, a short list of things to leave out, and the rejection risk. Two of its pages disagree on whether the limit is 100 characters or 100 bytes. Everything quoted below comes from pages we fetched on 29 October 2026; none of it is inference.

The App Store Connect reference page for platform version information describes the field itself: "One or more keywords (each greater than two characters) describing your app. You can provide up to 100 bytes of content. Your app is searchable by app name and company name, so you shouldn't duplicate these values in the keyword list. Names of other apps or companies aren't allowed."

Three things in that sentence carry weight. Each keyword must be longer than two characters. Your name and company name already rank, so repeating them wastes bytes. And other apps' names are not merely discouraged: Apple writes that they "aren't allowed".

Apple's page on creating your product page gives the format: "Keywords are limited to 100 characters total, with terms separated by commas and no spaces. (Note that you can use spaces to separate words within keyword phrases. For example: Property,House,Real Estate.)"

So a comma costs you a byte and a space after a comma costs you another for nothing. Spaces inside a phrase are fine when the phrase is really one term.

The same page lists what to avoid:

What Apple says to avoid	Apple's wording
Plurals	"Plurals of words that you’ve already included in singular form"
Categories and the word "app"	"Names of categories or the word “app”"
Repeats	"Duplicate words"
Special characters	"Special characters — such as # or @ — unless they’re part of your brand identity. Special characters don’t carry extra weight when users search for your app."

Then the harder list, which is about getting through review rather than ranking well: "Improper use of keywords is a common reason for App Store rejections. Do not use the following in your keywords: Unauthorized use of trademarked terms, celebrity names, and other protected words and phrases; Terms that are not relevant to the app; Competing app names; Irrelevant, inappropriate, offensive, or objectionable terms".

Guideline 2.3.7 of the App Review Guidelines says the same thing in Apple's review voice: "Choose a unique app name, assign keywords that accurately describe your app, and don’t try to pack any of your metadata with trademarked terms, popular app names, pricing information, or other irrelevant phrases just to game the system." It adds a power most makers do not expect: "Apple may modify inappropriate keywords at any time or take other appropriate steps to prevent abuse." If a rejection has already landed on you, our guide to a guideline 2.3.7 metadata rejection walks through what to change.

Two more lines from the product page guide your choices. On which words to pick: "Consider the trade-off between ranking well for less common terms versus ranking lower for popular terms." And on a field people often fill with keywords by mistake: "keep in mind that promotional text doesn’t affect your app’s search ranking so it should not be used to display keywords."

One loose end: the reference page says 100 bytes, the product page says 100 characters. For plain English they are the same number, and for anything else they are not. Our guide 100 characters or 100 bytes quotes both and works out what each means outside English.

What Apple does not write down

Apple does not say which of your localizations a storefront's search reads. On 27 August 2026 we measured one of our apps across 27 storefronts and found that most of them read a localization we had not aimed at them. That changes how much keyword room you actually have, and it decides where a phrase has to sit.

Here is what our measurement found about which localization each storefront read:

Storefront	Localization its search read (measured 2026-08-27)
23 of the 26 storefronts outside the UK	the English (U.K.) keyword field
United States	the Spanish fields
Canada	the French fields
Japan	neither English field

The second finding is about phrases. Apple matched each query against one localization at a time. We built nine test pairs, each joining a word from one localization to a word from another; all nine returned nothing, while each word on its own ranked. So a phrase matches as a phrase only when the whole phrase sits inside one localization's name, subtitle and keyword field. You cannot assemble a phrase out of two languages' fields.

The third finding is about position. A word reached through a foreign localization ranked far lower than a word in the storefront's own language:

Word and where it ranked	Measured position (2026-08-27)
English (U.K.) word in Germany, the Netherlands, Denmark, Ukraine	69th to 146th
Spanish word in Mexico	6th
Spanish word in Spain	15th
U.S. English word in the U.S. storefront	did not rank at all

That last row matters most. A word in the keyword field is not a promise of a match. Our U.S. English word sat in the field and returned nothing in the U.S. storefront on that day.

Taken together, the practical reading is this. Every extra localization a storefront reads is extra keyword room, so fill it with words that do not repeat the ones in your main localization. Keep each phrase whole inside one localization. And expect a borrowed-language word to rank, if at all, far down the list. The full study, with the method and every storefront, is in our cross-localization research, and the localization planner shows which fields a given storefront reads.

A worked example

Take a fictional habit-tracking app called "Steady: Habit Tracker" with the subtitle "Daily routine and streaks". The name and subtitle already spend six words: steady, habit, tracker, daily, routine, streaks. Now put twelve candidate keywords through the rules above and watch a third of them fall out before they cost a byte.

Candidate	Keep or drop	Reason
habits	drop	plural of "habit", already in the name
streak	drop	the subtitle already has "streaks"
goals	keep	new word
reminder	keep	new word
planner	keep	new word
checklist	keep	new word
journal	keep	new word
mood	keep	new word
routine	drop	already in the subtitle
app	drop	Apple advises against the word "app"
motivation	keep	new word
self care	keep	a phrase, so the space inside it is allowed

Before the rules, the list read: habits,streak,goals,reminder,planner,checklist,journal,mood,routine,app,motivation,self care

After the rules, the field reads: goals,reminder,planner,checklist,journal,mood,motivation,self care

That is 66 characters and 66 bytes, which leaves 34 bytes for words you have not thought of yet. The four words you dropped bought you that room, and none of them would have added a thing.

Keyword field, name and subtitle together

Treat the three fields as one list with no repeats. The name and subtitle carry your one phrase, because Apple says the app is searchable by name and because a phrase only matches when it sits whole in one localization. The keyword field then carries single words that combine with that phrase, which is why repeating a name word there buys nothing.

Work in this order. First pick the phrase you want to own and put it in the name or subtitle, inside the character limits for each field — our character limits reference lists them. Then write down every word those two fields already contain, plurals included. Then build the keyword list from words that are not on that list.

Before a word earns its bytes, check that anyone searches for it. Our keyword popularity estimator gives a free estimate from Apple's search suggestions and states its error, which helps separate a word people type from a word only you would type. Apple's own advice is the same trade-off in different words: rank well for less common terms, or rank lower for popular ones.

Finally, repeat the whole exercise for each localization a storefront reads, and keep the lists apart. If the U.S. storefront reads your Spanish fields, a Spanish word repeated in both the Spanish subtitle and the Spanish keyword field is a wasted byte in the U.S. too.

Questions

Is the keyword field 100 characters or 100 bytes?

Apple's two pages disagree: the App Store Connect reference page says "up to 100 bytes of content" while the product page guide says "limited to 100 characters total". For plain English text the two counts match. For accented or non-Latin words they do not, and our guide on 100 characters or bytes covers the difference.

Should I put phrases or single words in the keyword field?

Mostly single words, because the field's job is to supply words that combine with the phrase in your name and subtitle. Use a space inside a keyword only when the phrase is genuinely one term, the way Apple's own example writes "Real Estate".

Does putting the same word in the subtitle and the keyword field help it rank?

Apple lists "Duplicate words" among the things to avoid and says your app is already searchable by name, so the second copy spends bytes for nothing. The same logic applies across two localizations that one storefront reads.

Can I use a competitor's app name if my app really is an alternative to it?

No. The App Store Connect reference states that "Names of other apps or companies aren't allowed", and Apple's product page guide lists competing app names among the causes of rejection. Apple also reserves the right to change inappropriate keywords itself.

Can I put keywords in the promotional text instead?

No. Apple writes that "promotional text doesn’t affect your app’s search ranking so it should not be used to display keywords." Promotional text is for news you want shown; search ignores it.