Understanding and Using Keywords on Amazon: A Comprehensive Guide for Self-Publishers
What Are Keywords and Why Do They Matter?
Keywords are specific words or phrases that potential readers type into Amazon's search bar when looking for books. These search terms are critical because they directly influence a book's visibility in Amazon's massive marketplace. When self-publishers select the right keywords, they increase the chances that their book will appear in front of interested readers. Essentially, keywords act as the connective tissue between your book and your audience—they are how your book gets discovered.
Whether you're launching a new release or revamping an existing title, keywords play a central role in discoverability. Unlike categories, which classify your book by genre or format, keywords give you a more flexible tool to target themes, settings, character types, emotions, tropes, and reader interests. Done correctly, keywords can help boost organic traffic, support advertising efforts, and even push your book up the bestseller charts. But done poorly, they can bury your title in obscurity or even lead to Amazon warnings.
In this guide, we'll walk through everything you need to know about keywords on Amazon—from avoiding competing keywords to using AI to generate keyword ideas, understanding category strings, Kindle Unlimited strategy, and more.
What Are Competing Keywords?
Competing keywords are search terms or phrases that are used so frequently across Amazon that ranking high for them becomes difficult, especially for newer or lesser-known books. These are often broad, single-word entries like "romance," "thriller," or "mystery." The competition for these keywords includes traditionally published books, bestsellers, and high-budget marketing campaigns.
To avoid competing keywords, authors should focus on long-tail keywords—specific multi-word phrases that better match a niche audience's search intent. For example, instead of using "romance," try "small town second chance romance" or "clean billionaire romance with secret baby." These have lower competition and higher relevance to the exact reader you're trying to attract.
How Amazon Uses Keywords
Amazon uses the seven keyword fields available to authors when uploading their books through Kindle Direct Publishing (KDP) to help determine where and how a book appears in search results and category recommendations. These keywords help Amazon match your book with customer queries typed into the search bar.
Amazon's algorithm is built to reward:
Relevance to customer searches
Sales velocity (how quickly your book is selling)
Customer behavior (clicks, time spent, reviews)
The keywords do not need to be repeated in your book's title or subtitle, but synergy across title, subtitle, keywords, and book description improves discoverability.
Why Deception Should Be Avoided
Using misleading keywords—such as including "Harry Potter" or "Stephen King" to attract attention—violates Amazon's metadata guidelines. Deceptive metadata can result in:
Removal of your book
Suspension of your KDP account
Loss of royalties
Amazon's bots and human moderators look for violations, especially in popular or trademarked phrases. Integrity in metadata not only keeps your book compliant but ensures you're reaching the right readers—those who are more likely to finish, enjoy, and review your book.
The Importance of Researching Your Keywords Before Selecting Them
Choosing keywords without research is like publishing a book without editing—it's risky and almost always ineffective. Research allows you to:
Find low-competition, high-relevance keywords
Identify phrases that real readers are actually searching
Evaluate which keywords are being used by successful books in your genre
Avoid wasted keyword slots on irrelevant or overused terms
Using Amazon's autocomplete function can help you generate ideas and assess their viability.
Using Similar Books to Find Keywords (Starting with Bestsellers)
A smart way to discover effective keywords is by examining books similar to yours, particularly bestsellers:
Start with the bestseller in your genre. Look at the book's product page.
Scroll down to "Product Details" to note the categories the book is listed under.
Examine the book's description and note recurring phrases and tropes.
Read reader reviews and questions—the language readers use can be rich with search terms.
Use the "Look Inside" feature to see terms or topics emphasized early in the book.
Work your way down from top sellers to mid-list and new releases. This gives a broader understanding of how successful authors in your genre structure their keywords and descriptions.
What Is a Category String and How Does It Relate to Keywords?
A category string is the full path that defines the genre and subgenre of a book in Amazon's catalog. For example: Books > Romance > Paranormal > Vampires
Keywords influence which categories Amazon assigns to your book beyond the two you can manually select. If you include keywords like "shifter romance" or "fated mates," Amazon may place you into niche categories that more closely match your content.
This is why including category-aligned phrases in your keyword fields increases the chance of being shown to the right audience.
How Many Keywords Amazon Allows and Their Required Structure
Amazon allows authors to input seven keyword fields, each up to 50 characters. These fields are not visible to customers but are used by Amazon's internal algorithms.
Do not repeat keywords across fields or include words already in your title or subtitle.
Use phrases rather than single words when possible.
Keyword Structure and the Role of Commas
Amazon's algorithm treats spaces as separators, not commas. Commas are unnecessary and can reduce keyword performance. Instead of typing: "romantic, suspense, mystery" — use: "romantic suspense mystery". This allows Amazon to match combinations such as "romantic suspense," "suspense mystery," or even "romantic mystery" more flexibly.
Kindle Unlimited's Impact on Keyword Strategy
Kindle Unlimited (KU) is Amazon's subscription service for readers. Books enrolled in KU get special visibility and promotional opportunities, such as inclusion in KU-specific recommendations.
Authors in KU benefit from targeting keywords that:
Appeal to voracious readers
Match popular binge-worthy subgenres (e.g., "reverse harem academy fantasy," "small town romance series")
Emphasize "series," "saga," or "episodic" in keyword strategies
Since KU readers often explore by genre or theme and consume multiple books per month, optimizing for read-through potential can increase page reads and royalties.
How Traditional Publishers Impact Keyword Competition
Traditionally published books often dominate broad categories and highly competitive keywords due to bigger marketing budgets, professional metadata teams, and high-volume traffic from outside Amazon. This creates keyword congestion for terms like "psychological thriller" or "gritty detective noir." Indie authors must use this information to position themselves strategically with more specific phrases like "female-led psychological thriller with unreliable narrator" or "slow-burn mystery in small town."
How AI Can Assist Keyword Creation from a Synopsis
Artificial Intelligence can quickly extract relevant phrases, genre identifiers, and themes from a long synopsis and turn them into optimized keyword suggestions.
Sample Prompt for ChatGPT or other AI tools:
"Analyze the following 300-word book synopsis and generate 20 optimized Amazon KDP keyword phrases that reflect genre, audience intent, tropes, and themes, avoiding overly competitive or trademarked phrases: [paste synopsis here]."
This saves time and provides diverse, tested options for experimentation.
Step-by-Step: How to Select and Upload Keywords to Amazon KDP
Write or paste your synopsis into an AI tool and use the prompt above to extract keywords.
Visit Amazon.com and start typing your genre's most common search terms into the search bar. Note the autocomplete suggestions — these are real searches readers are making.
Cross-reference your AI-generated keyword list against Amazon's autocomplete suggestions. Keep phrases that appear in both sources — they represent search terms with both relevance and actual reader demand.
Check your keywords against the forbidden terms list in Amazon's KDP metadata guidelines. Remove any trademarked names, author names, or misleading terms.
Build your final list of seven keyword phrases. Each should be under 50 characters, use spaces not commas, and target different aspects of your book — tropes, setting, character type, theme, subgenre, and comparative positioning.
Log in to kdp.amazon.com and navigate to your book's detail page. Scroll to the Keywords section.
Enter one phrase per keyword field. Do not duplicate words across fields or repeat words already in your title or subtitle — Amazon's algorithm already factors those in.
Save and publish. Your keywords take effect immediately on new books; updates to existing books typically index within 24–72 hours.
Monitor sales data over the following 2–4 weeks. If you see no improvement in visibility or rank, test new keyword phrases in one or two fields at a time, noting the date of each change to track impact.
Keyword Research Tools Worth Knowing
Beyond Amazon's autocomplete and AI tools, several paid tools are designed specifically for KDP keyword research:
Publisher Rocket — searches Amazon's actual search data to show search volume and competition for specific keyword phrases. The most widely used dedicated KDP keyword research tool among indie authors.
K-lytics — provides genre-level market data including keyword trends. More useful for broad genre strategy than individual keyword optimization.
Amazon's own Search Term Report — if you run Amazon Ads, your Search Term Report shows exactly which keywords are triggering your ads and which are converting to sales. This is the most accurate keyword performance data available and directly informs your organic keyword choices.
ScribeCount Author OS:
Connecting Keywords to Sales Results
Keywords drive visibility. Visibility drives sales. ScribeCount's Sales Dashboard shows you the sales result of your keyword and metadata strategy — real royalty data from KDP updated regularly. When you update keywords, note the date in ScribeCount's notes or track it against your Historical view. A meaningful keyword improvement typically shows up as a sustained increase in daily sales or Kindle Unlimited page reads within two to four weeks. ScribeCount doesn't show keyword-level attribution directly — Amazon doesn't expose that data outside of Ads. But it shows the aggregate sales effect of your full metadata strategy, which is ultimately what matters.
Conclusion
Keywords are one of the most powerful free tools available to indie authors on Amazon. Seven fields, 50 characters each, changed as often as you want at no cost. The investment is time and research — not money.
Research your keywords before you publish. Use AI to expand your options. Use Amazon's autocomplete to validate demand. Avoid broad terms where traditional publishers dominate. Target the specific phrases your ideal reader is actually searching for. And monitor the results so you know when something is working and when it's time to test something new.
The difference between a keyword strategy built on research and one built on guesswork is often the difference between a book that finds its audience and one that doesn't.
- Randall
