Last reviewed by Robert Prime, July 2026
Amazon gives every KDP book seven keyword boxes, each holding a short phrase of up to 50 characters, and they are one of the few discoverability levers you control completely. The method that works is simple: fill each box with a distinct search phrase real readers type — found using Amazon's own search-bar suggestions — written in natural word order, with no repetition of words already in your title or categories, and none of the banned terms (quality claims, "free", "Kindle Unlimited", other authors' names) that can get a book flagged.
That's the whole game in one paragraph. The rest of this guide shows you how to do it properly: what Amazon actually indexes, a research method that takes under an hour, and the mistakes that quietly waste boxes — or worse, trip Amazon's metadata rules.
TL;DR — Key Takeaways
- Seven boxes, roughly 50 characters each. Every box is a separate phrase; you don't need commas, and quotation marks actively hurt (Amazon treats them as exact-match strings).
- Don't repeat words from your title, subtitle or categories. Amazon already indexes those — a repeated word is a wasted box.
- Use reader language, not author language. Amazon's own guidance suggests keywords for setting ("Victorian London"), character type ("single dad", "strong female lead"), plot theme ("enemies to lovers", "coming of age") and tone ("feel-good", "dark").
- Research with Amazon's search bar. The autocomplete dropdown is a live feed of what shoppers actually type. Mine it in an incognito window.
- Banned: subjective quality claims ("best thriller ever"), time-sensitive words ("new", "on sale"), other authors' or books' names, Amazon programme names ("Kindle Unlimited", "KDP Select"), and HTML or quote marks.
- Keywords are editable any time — treat them as an experiment, not a tattoo.
What do KDP keywords actually do?
When a reader types a phrase into Amazon's search bar, Amazon decides which books qualify to appear at all, then ranks the qualifiers. Your seven keyword phrases — together with your title, subtitle, and categories — determine the first part: whether your book is even in the running for a given search. Sales history and conversion then decide how high it ranks.
Two practical consequences follow. First, keywords can only put you in the race; they can't win it. A book that doesn't convert won't hold a ranking no matter how clever its metadata. Second, a search phrase your book isn't indexed for is a race you never entered. Seven boxes at ~50 characters is a decent amount of indexing surface — wasting it on words Amazon already knows about you is the most common mistake in self-publishing metadata.
It's worth saying what keywords are not: they're not tags readers see, they're not Amazon Ads targeting (that's set separately inside the ads console — see our Amazon ads guide), and they're not a ranking cheat code.
What should go in the seven boxes?
Amazon's own help page is unusually direct here. It recommends keywords that capture the things readers search for but that don't fit in your title:
| Keyword type | Examples |
|---|---|
| Setting | Victorian London, Cornish village, space colony |
| Character type | single dad, reluctant detective, veteran |
| Character role | strong female lead, antihero |
| Plot theme | enemies to lovers, redemption, survival |
| Story tone | dark psychological, feel-good, gripping |
For non-fiction, think in terms of the problem being solved ("meal prep for beginners"), the audience ("retirement planning for the self-employed"), and the format ("workbook", "step by step").
Within each box, write phrases in natural reading order — Amazon's guidance explicitly says "military science fiction" works, "fiction science military" doesn't. You can fit more than one concept in a box's 50 characters, and individual words within a box combine to match searches, so a box like cosy village mystery female detective covers several related searches at once. Don't stuff it with commas or repeats; write it the way a reader would say it.
How do I research keywords without paid tools?
You don't need software for a solid first pass. The best free research tool is Amazon itself.
1. Open Amazon in a private/incognito window (so your own browsing history doesn't skew suggestions) and make sure you're on amazon.co.uk if UK readers are your market.
2. Type your seed phrase slowly and record the autocomplete suggestions. Those suggestions are drawn from real shopper searches — it's the closest thing to Amazon handing you its query log. Work through the alphabet: "cosy mystery a…", "cosy mystery b…", and so on.
3. Check the results page for each candidate. Two things tell you whether a phrase is worth a box: are the top results books like yours (if not, Amazon interprets that phrase differently than you do), and are they selling (check a few sales ranks)? A phrase where similar books sell at ranks between roughly 10,000 and 100,000 is often the sweet spot — real demand, beatable competition.
4. Fill seven boxes with seven genuinely different phrases. If two candidate phrases share their important words, keep one and spend the other box elsewhere.
Repeat the exercise for each format — and note Amazon's advice to keep keywords consistent between your ebook and paperback so both editions surface for the same searches.
What will get your keywords rejected — or your book flagged?
Amazon's metadata guidelines prohibit a specific list of practices, and enforcement is automated enough that it's not worth testing:
- Reference to other authors or books. Putting "Richard Osman" in a keyword box is a metadata violation, not a growth hack.
- Subjective quality claims — "best", "bestselling", "award-winning" (unless the award is real and in your book's actual metadata elsewhere).
- Time-sensitive claims — "new", "on sale", "available now".
- Amazon programme names — "Kindle Unlimited", "KDP Select", "Prime".
- The word "free", price claims, or anything misleading about the book.
- Quotation marks and HTML tags. Quotes force exact-string matching and shrink your reach; HTML is simply prohibited.
A metadata violation can hold your book in review, or in repeat cases contribute to account-level trouble — the same review pipeline that catches formatting problems. If your book has ever been stuck in review, our guide to KDP rejections and how to fix them covers the process.
How often should I change my keywords?
Whenever you have a reason to — they're editable from your Bookshelf at any time and changes typically propagate within about 72 hours. Sensible triggers:
- A box is doing nothing. You can't see per-keyword data directly, but if sales are flat and your also-boughts are misaligned with your genre, poor indexing is a suspect.
- Seasonal or trend shifts. "Christmas romance" earns its box in October, not February.
- You've run Amazon Ads. Your ad console's search-term report shows which real queries converted — promote the winners into your keyword boxes. This is the single best feedback loop, and it's covered in our healthy ad spend guide.
Change one or two boxes at a time and give each change a couple of weeks, or you won't know what worked.
Keywords won't fix a book that doesn't convert
A final note of proportion. Keywords decide whether you appear; your cover, blurb, price, reviews and — yes — your interior formatting decide whether the click becomes a sale, and the sale becomes a ranking. Amazon's Look Inside sample is part of that conversion surface: a manuscript with broken indents or inconsistent chapter openings loses readers on page one. If yours needs sorting, our formatting service turns a manuscript into a KDP-ready PDF and EPUB from £69.
Get the fundamentals converting first; then keyword research compounds instead of papering over cracks.
Frequently Asked Questions
How many keywords does Amazon KDP allow?
Seven keyword boxes per book, each holding a phrase of up to 50 characters including spaces. All seven are optional, but there's no reason to leave one empty — each box is free indexing surface.
Should I repeat my title words in my KDP keywords?
No. Amazon already indexes your title, subtitle and category information, so repeating those words wastes a box. Use the seven boxes for reader search phrases that don't appear anywhere else in your metadata — setting, character types, themes, tone, audience.
Can I use a comma-separated list inside one keyword box?
You can, but you usually shouldn't. Words within a box combine to match searches anyway, so natural phrases ("cosy village mystery female detective") do the same job while also matching the full phrase as typed. Amazon's guidance favours logical word order over comma-stuffing.
Can I put another author's name in my keywords?
No — referencing other authors, their books, or brands you're not affiliated with violates Amazon's metadata guidelines and can get your book flagged or blocked. If you want to reach fans of a comparable author, do it through Amazon Ads product targeting instead, where targeting a rival's product page is allowed.
How long do keyword changes take to show on Amazon?
Metadata edits generally go live within about 72 hours, though indexing for search can take a little longer to settle. Change one or two boxes at a time and judge results over weeks, not days.
About the Author
Robert Prime is a self-published author, veteran e-commerce strategist, and the founder of publishing.co.uk. With over 25 years in digital business — including running the Amazon advertising agency MrPrime.com, he brings a practical, numbers-first perspective to self-publishing. After navigating the formatting and marketing of his own book, Google. Panic. Repeat., he built publishing.co.uk to help UK authors avoid the same pitfalls. He is co-owner of the LoveReading.co.uk network and a member of the Forbes Business Council.
