How to Fill Your App Store Keyword Field: AI-Generated 100-Character Sets

100 characters. That's your entire keyword budget.

The App Store gives you exactly 100 characters to define how people find your app through search. Not 100 words — 100 characters, including commas. Every character you waste is a keyword you're not ranking for. Every bad keyword you include is a good one you had to leave out.

Most indie developers fill this field once at launch, guess at a few terms, and never touch it again. That's leaving downloads on the table. Over 65% of App Store installs come from search, and your keyword field is the single biggest lever you have for search visibility.

We built an AI keyword optimizer in Apsity that generates complete 100-character sets based on real ranking data, competitor analysis, and difficulty scoring. Here's how the whole system works — and how to use it.

App Store keyword field rules

Before talking about optimization, you need to know Apple's rules. Get these wrong and you're wasting characters:

• Comma-separated, no spaces after commas. Write budget,tracker,expense, not budget, tracker, expense. Each space after a comma costs you one character for nothing.
• No plurals. Apple's search algorithm automatically matches singular to plural. Writing "budgets" when you could write "budget" wastes a character.
• Don't repeat your app name or subtitle. Apple already indexes those fields separately. Duplicating a word from your name into keywords is a wasted slot.
• Don't include your category name. "Finance" or "Productivity" — Apple indexes your primary and secondary categories automatically.
• No special characters or URLs. Stick to letters, numbers, and commas.
• Use all 100 characters. A keyword field with 72 characters means you left 28 characters — potentially 3 or 4 keywords — on the table.

These rules sound simple, but applying them perfectly while maximizing keyword coverage is where it gets hard. You need to know which keywords to include, and that requires data.

The problem with manual keyword research

Here's what manual keyword optimization looks like. You open App Store Connect. You look at your current keywords. You wonder: are these working? You don't know because ASC doesn't show you keyword rankings.

So you search the App Store manually. Type in "budget tracker" and see where your app appears. Maybe it's at position 47. Is that good? Hard to say without knowing the difficulty. A rank of 47 for a difficulty-20 keyword means you have room to climb. A rank of 47 for a difficulty-85 keyword means you'll probably never break the top 10.

Then there's the competition angle. You don't know what keywords your competitors are targeting. You don't know if they changed their metadata last week, potentially shifting rankings in the entire category. You're optimizing blind.

This is the gap we wanted to close with Apsity's keyword tools: make keyword decisions based on real data instead of guesswork.

How Apsity tracks keyword performance

Every day at 3 AM KST, a cron job checks your app's ranking for every tracked keyword. It queries the iTunes Search API for each keyword term, finds your app in the results, and records the position. If your app isn't in the top 200, it records "Not ranked".

Over time, this builds a ranking history. You can see trends: "budget tracker" went from #35 to #18 over three weeks. Or "expense log" dropped from #12 to #45 after a competitor changed their subtitle. These trends are what inform keyword decisions.

Each keyword also gets a difficulty score on a 0–100 scale. We calculate this based on the strength of the top-ranked apps for that term — their rating counts, review volumes, and how long they've held their positions.

The difficulty score is the key filter. If you're an indie developer with 200 ratings, spending a keyword slot on a difficulty-85 term is almost always a waste.

What the AI optimizer actually does

The AI keyword optimizer runs as part of the daily insight generation. When you open the Keywords tab and click Generate Optimized Set, here's the pipeline:

1. Current keyword analysis. The AI reads your existing keyword field and evaluates each term. Keywords with difficulty 70+ are flagged red — they're probably not helping. Keywords where you rank beyond position 150 are flagged as replacement candidates.
2. Competitor keyword extraction. It analyzes the metadata (names, subtitles, descriptions) of your tracked competitors. Words that appear frequently across successful indie apps in your category but are absent from your keywords become candidates.
3. Review keyword mining. User reviews contain search signals. If 30 reviews mention "minimalist" but that word isn't in your keywords, it's a gap. The AI extracts recurring terms from your reviews and competitor reviews.
4. Low-competition filtering. All candidate keywords are checked against difficulty scores. Anything above difficulty 70 is dropped unless you already rank in the top 20 for it. The goal is to find terms where you can realistically compete.
5. 100-character assembly. The AI generates a complete keyword string targeting 90–100 characters. It follows all App Store rules: no spaces after commas, no plurals, no duplication with your app name or category. Every character is accounted for.

The entire process uses Claude Sonnet as the reasoning engine. We pass it structured data — rankings, difficulty scores, competitor metadata, review excerpts — and it returns a keyword set with explanations.

Understanding the output

The optimizer doesn't just give you a keyword string. It shows you exactly what changed and why. The output includes:

• Removed keywords — which terms from your current set were dropped, and the reason (e.g., "difficulty 82, ranked #167 — not competitive").
• Added keywords — which new terms were added, their difficulty score, and why they were chosen (e.g., "difficulty 23, 3 indie competitors rank top 10 — realistic target").
• Kept keywords — terms that stayed because they're already performing well.
• Character count — the total length of the new keyword string, typically 90–100 characters.

This transparency matters. You shouldn't blindly paste AI-generated keywords. Read the reasoning, check whether it makes sense for your app, and adjust if needed. The AI has data but you have context about your app that data alone can't capture.

Copy, paste, and update

If you're happy with the generated set, there's a copy button on the card. Click it, open App Store Connect, navigate to your app's version page, find the keyword field, and paste. Submit for review or save as-is if you're just updating keywords (keyword changes don't require a new app version).

One common mistake: forgetting to remove the old keywords before pasting. The keyword field should contain only the new set. Don't append — replace.

When to re-optimize

Keywords aren't a one-time thing. The App Store is competitive and rankings shift constantly. We recommend re-running the optimizer every 2–3 weeks, or immediately after any of these events:

• A competitor changes their metadata. Apsity detects this automatically and generates a RANK_DROP_DIAGNOSIS insight if your rankings shifted.
• Your rankings drop significantly. A 10+ position drop on a key term means something changed in the competitive landscape.
• You launch an update. New features might warrant new keywords. If you added a "widget" feature, "widget" should probably be in your keywords.
• Seasonal trends. "tax" is a much better keyword in March than in August. "gift" peaks in December. Adjust accordingly.

The optimizer accounts for your historical ranking data, so each run builds on what came before. It won't suggest keywords you already tried and failed to rank for — unless the competitive landscape has changed enough to make them viable again.

Real example: a finance app optimization

Here's a real scenario we encountered during development. A finance app had this keyword field:

budget,money,expense,tracker,finance,savings,spending,bills,wallet,personal finance

That's 82 characters — 18 wasted. The terms "finance" (already the app category) and "money" (difficulty 88) were not helping. "Personal finance" (difficulty 76) was also a losing battle for an indie app with 180 ratings.

After running the optimizer:

budget,expense,tracker,savings,spending,bills,wallet,receipt,cashflow,frugal,allowance

That's 97 characters. "Finance", "money", and "personal finance" were removed. "Receipt" (difficulty 31), "cashflow" (difficulty 28), "frugal" (difficulty 12), and "allowance" (difficulty 19) were added. All four new terms had indie apps ranking in the top 10 — a realistic target.

Two weeks later, the app ranked in the top 15 for "frugal" and "cashflow". Small keywords, but they contributed real downloads from users who were actually looking for that type of app.

The 100-character mindset

Think of the keyword field as premium real estate. Every character has a cost — including it means excluding something else. The optimizer's job is to maximize the value per character: drop high-difficulty terms you'll never rank for, add low-difficulty terms where you can realistically compete, and use every character available.

You can do this manually if you have the data. Apsity makes it faster by tracking rankings daily, scoring difficulty automatically, monitoring competitors, and letting the AI do the combinatorial work of fitting the best keywords into exactly 100 characters.

Keywords are the most underused growth lever for indie apps. Most developers spend hours on design and features but five minutes on keywords. Flip that ratio — even a little — and the results show up in your download numbers.