Make Your Book More Discoverable with Keywords (2025)

Here's a frustrating truth about selling books on Amazon:

Your book could be exactly what thousands of readers are searching for, but if they can't find it, it doesn't exist.

Over 4.5 million self-published titles flood Amazon KDP every year. That's roughly 12,000 new books hitting the marketplace daily. In that ocean of content, discoverability isn't just important. It's everything.

The secret weapon? Amazon backend keywords.

These hidden search terms work behind the scenes to connect your book with readers who are actively looking for exactly what you've written. Get them right, and Amazon's algorithm becomes your 24/7 sales team, surfacing your book to the perfect audience. Get them wrong (or ignore them entirely), and you're invisible.

Over 50% of Kindle's Top 400 books in 2023 were self-published. That's a 53% increase from 2022. More than 2,000 self-published authors earned over $100,000 in royalties in 2024. The opportunity is real, but only for authors who understand how Amazon's search system works.

This guide breaks down everything you need to know about Amazon backend keywords for books, from basic setup to advanced optimization strategies that actually move the needle.

New to selling on Amazon? Start with our What is Amazon FBA? guide for the fundamentals. Already familiar with Amazon's ecosystem and want to dive deeper into keyword strategy? Check out our Amazon Keyword Research guide.

What Are Amazon Backend Keywords for Books?

Amazon backend keywords (also called search terms or hidden keywords) are phrases you add to your KDP listing that help Amazon's algorithm understand what your book is about.

Unlike keywords in your title or description, backend keywords are invisible to shoppers. They exist purely to help Amazon's search engine match your book with relevant customer searches.

Here's the critical distinction:

When someone types "cozy mystery small town bakery" into Amazon's search bar, the algorithm scans titles, descriptions, categories, and backend keywords to find the best matches. Your backend keywords give you seven extra opportunities to capture relevant searches without cluttering your visible listing.

Why Backend Keywords Matter for Book Sales

Think of Amazon's search system like a matchmaking service. Readers describe what they want. Amazon tries to find the perfect book. Your job is to give Amazon as much information as possible about your book so it can make accurate matches.

Without proper backend keywords:

• Your book only appears for searches that match your title and description
• You miss long-tail keyword opportunities (specific phrases with less competition)
• Competitors who optimize their keywords outrank you for relevant searches

With strategic backend keywords:

• Your book surfaces for a wider range of relevant searches
• You capture niche reader segments looking for specific themes, tropes, or topics
• Amazon's algorithm gains confidence about your book's relevance, improving overall ranking

The math is simple. More relevant searches mean more impressions. More impressions mean more clicks. More clicks (with the right audience) mean more sales.

How Amazon's Book Search Algorithm Works

Before optimizing your keywords, you need to understand how Amazon decides which books to show for any given search.

Amazon's A10 algorithm considers multiple factors when ranking search results:

1. Keyword Relevance

Does your book contain the words the customer searched for? Amazon checks:

• Title and subtitle
• Book description
• Backend search terms
• Category assignments

If a keyword isn't present anywhere in your metadata, you won't appear for that search. Period.

2. Sales Velocity

How many copies has your book sold recently? Books that sell well get ranked higher because Amazon's algorithm assumes popular books are more likely to satisfy customers.

This creates a chicken-and-egg problem: you need visibility to get sales, but you need sales to get visibility. Backend keywords help solve this by capturing more search traffic from day one.

3. Conversion Rate

When shoppers click on your book, do they buy it? High click-to-purchase ratios signal to Amazon that your book delivers on its promise. This is why keyword accuracy matters. Appearing for irrelevant searches might get clicks, but those visitors won't convert, and your ranking will suffer.

4. Customer Engagement

Reviews, ratings, "Look Inside" previews, and even how long shoppers spend on your product page all factor into Amazon's ranking decisions.

The Relevance Hierarchy

Not all keyword placements carry equal weight:

1. Title keywords have the strongest impact on ranking
2. Backend keywords are weighted nearly as heavily as title keywords
3. Description keywords influence ranking but carry less weight
4. Category selection determines which competitive set you're compared against

This hierarchy explains why backend keywords are so valuable. They're almost as powerful as title keywords, but they're invisible to shoppers, giving you freedom to target terms that would look awkward in your title.

Where to Add Backend Keywords in KDP

Amazon KDP gives you seven keyword fields, each accepting around 50 characters (though the limit varies slightly by marketplace). Here's exactly how to access and update them:

Step-by-Step: Adding Backend Keywords

1. Log into KDP: Go to kdp.amazon.com and sign in
2. Go to your Bookshelf: Click the "Bookshelf" tab to see all your titles
3. Select your book: Click the ellipsis button (…) next to your book
4. Edit book details: Select "Edit eBook details" (or paperback/hardcover)
5. Find the Keywords section: Scroll down to the "Keywords" area
6. Enter your keywords: Fill all seven fields with strategic keyword phrases
7. Save and publish: Click "Save and Continue," then publish your changes

Changes typically take 24 to 72 hours to reflect in Amazon's search results. Plan your keyword updates accordingly, especially around book launches or promotions.

The 7 Keyword Fields: How to Use Them

Each keyword field should contain a complete phrase, not just a single word. Amazon recommends thinking of these as "search phrases" rather than individual keywords.

Good approach:

• Field 1: cozy mystery small town
• Field 2: amateur sleuth bakery
• Field 3: clean mystery no swearing
• Field 4: female detective series
• Field 5: beach read mystery
• Field 6: cat lover mystery
• Field 7: feel good crime fiction

Bad approach:

• Field 1: mystery
• Field 2: crime
• Field 3: detective
• Field 4: investigation
• Field 5: sleuth
• Field 6: book
• Field 7: novel

Single words are too broad and face massive competition. Phrases capture specific reader intent and have better conversion rates.

How to Research Kindle Keywords That Actually Work

Finding profitable Kindle keywords requires a systematic approach. Here's the proven process:

Method 1: Amazon Autocomplete (Free)

The simplest method, often overlooked by new authors.

1. Go to Amazon.com
2. Select "Kindle Store" or "Books" from the category dropdown
3. Type a word related to your book's genre or topic
4. Don't press Enter. Look at the autocomplete suggestions
5. Add letters after your keyword to discover more variations

Example: Type "romance" and you'll see:

• romance books
• romance novels
• romance kindle unlimited
• romance enemies to lovers

These suggestions represent actual searches that real customers type. Amazon wouldn't suggest them otherwise.

Method 2: Competitor Analysis

Why guess when you can see what's already working?

1. Find 5 to 10 successful books in your genre (Amazon BSR under 10,000, 50+ reviews)
2. Note their titles, subtitles, and descriptions
3. Identify common phrases and themes
4. Search for those phrases on Amazon to see what else ranks

If top-selling books in your genre consistently mention "clean romance" or "no cliffhangers," those are likely high-value keywords worth targeting.

Method 3: Category Deep-Dives

Amazon's category system reveals what readers are looking for.

1. Navigate to the Kindle Store
2. Browse into your genre's subcategories
3. Note the most specific subcategory names (these are often searchable keywords)
4. Check the "Customers also bought" section for pattern recognition

Subcategories like "Small Town & Rural Romance" or "Culinary Cozy Mysteries" tell you exactly what specific niches readers are browsing.

Method 4: Use Keyword Research Tools

Manual research works, but it's time-intensive. Dedicated tools accelerate the process:

For book-specific keyword research:

• Publisher Rocket (shows search volume and competition)
• KDP Rocket (Kindle-focused keyword data)

For general Amazon keyword research:

• The Launch Fast Keyword Research Suite provides competitive analysis across Amazon's entire ecosystem, showing you which keywords drive real conversions.

The Launch Fast PPC Insights Tool takes keyword research further. Enter your book's ASIN plus competitor ASINs to get:

• Complete keyword landscape for your niche
• Search volume and competition metrics
• Gap analysis showing keywords competitors rank for that you don't

This approach works for any Amazon product category, including books. The same keyword research principles that help physical product sellers dominate their niches apply directly to KDP.

What Makes a "Good" Kindle Keyword?

Before adding any keyword to your backend fields, evaluate it against these criteria:

The sweet spot: keywords with 500 to 5,000 monthly searches, low to medium competition, and high relevance to your book's content.

Amazon Backend Keywords Best Practices

Amazon provides specific guidance on what works and what to avoid. Follow these rules to stay compliant and maximize effectiveness.

Do: Use These Keyword Types

Setting and location keywords:

• Colonial America
• Victorian England
• Small town Texas
• Pacific Northwest

Character type keywords:

• Single dad
• Military veteran
• Strong female lead
• Billionaire hero

Theme and plot keywords:

• Coming of age
• Second chance romance
• Enemies to lovers
• Revenge plot

Tone and style keywords:

• Feel good
• Dark and gritty
• Clean romance
• Page turner

Reader preference keywords:

• No cliffhangers
• Standalone
• Series complete
• Clean language

Don't: Avoid These Keyword Mistakes

Amazon explicitly prohibits certain keyword practices. Violations can result in your book being suppressed in search results or removed entirely.

Never use:

• Quality claims: "Best novel ever," "award winning" (unless verified)
• Time-sensitive language: "New release," "on sale now," "available today"
• Competitor brand names: Don't use other author names or book titles
• Amazon program names: "Kindle Unlimited," "KDP Select," "Prime Reading"
• Misleading information: Any keywords that don't accurately describe your book
• Redundant information: Words already in your title or categories
• Generic terms: "Book," "ebook," "Kindle" (every book has these by default)

Formatting Tips

• No commas needed: Amazon separates keywords automatically with spaces
• Use logical order: "Military science fiction" works better than "fiction military science"
• Include alternate spellings: "Hanukkah" and "Chanukah" if relevant
• Think like a reader: What would someone searching for your book actually type?

Advanced Keyword Strategies for Authors

Once you've covered the basics, these advanced tactics can give you an edge.

Strategy 1: Target Reader Problems, Not Just Topics

Instead of only targeting genre keywords, think about what problems your book solves for readers.

For fiction:

• "Books to read when sad"
• "Escape reality books"
• "Quick weekend read"
• "Beach vacation books"

For nonfiction:

• "Learn Spanish fast"
• "Budget meal planning"
• "Anxiety self help"
• "Career change guide"

These problem-focused keywords capture readers at the moment they're deciding what to buy.

Strategy 2: Leverage "Also Bought" Patterns

Amazon's recommendation engine is a goldmine of keyword intelligence.

1. Find a successful book similar to yours
2. Check the "Customers who bought this also bought" section
3. Analyze what those related books have in common
4. Target keywords that connect your book to that cluster

If your cozy mystery keeps appearing alongside books about "cat cafe mysteries," that's a signal to include cat-related keywords in your backend.

Strategy 3: Seasonal Keyword Rotation

Update your keywords based on seasonal search patterns:

• Holiday themes: Add "Christmas romance" or "Halloween thriller" during relevant seasons
• Summer reading: "Beach read," "vacation book," "summer page turner"
• Back to school: For educational nonfiction
• New Year: Self-improvement and goal-setting keywords

Set calendar reminders to update keywords 4 to 6 weeks before peak seasons.

Strategy 4: Track and Iterate

Keywords aren't "set and forget." Monitor your book's performance and adjust.

Check monthly:

• Which keywords are driving traffic (check Amazon Ads search term reports if running ads)
• Your book's ranking for target keywords
• Competitor keyword strategies (have they changed?)

The Launch Fast Rank Tracker helps authors and Amazon sellers monitor organic keyword positions over time, showing whether your optimization efforts are paying off.

Backend Keywords vs. Amazon Ads: How They Work Together

Backend keywords and Amazon Advertising aren't either/or strategies. They work best together.

The Synergy Effect

1. Backend keywords help you rank organically for relevant searches
2. Amazon Ads let you bid on keywords and get immediate visibility
3. Sales from ads improve your organic ranking
4. Higher organic ranking reduces your dependency on paid ads

Using Ads to Discover Keywords

Amazon's Sponsored Products campaigns reveal which keywords actually convert buyers.

1. Run an auto campaign for 2 to 4 weeks
2. Download your Search Term Report from Amazon Ads
3. Identify terms with high impressions and good conversion rates
4. Add converting terms to your backend keywords

This approach uses real purchase data to inform your keyword strategy, rather than relying on theoretical search volume estimates.

PPC Keyword Integration

The Launch Fast PPC Insights tool connects your advertising data with organic keyword tracking:

• See which paid keywords are improving organic rank
• Identify opportunities where organic ranking could replace ad spend
• Find keyword gaps where competitors are advertising but you're not

For authors running Amazon Ads, this integration closes the loop between paid and organic discoverability.

Common Backend Keyword Mistakes to Avoid

Even experienced authors make these errors. Avoid them for better results.

Mistake 1: Keyword Stuffing

Cramming every possible keyword into your fields might seem smart, but Amazon's algorithm detects unnatural patterns. Focus on 7 high-quality, relevant phrases rather than trying to game the system.

Mistake 2: Ignoring Long-Tail Keywords

New authors chase broad terms like "romance" or "thriller" and wonder why they don't rank. Those keywords have millions of competing books. Long-tail phrases like "small town veterinarian romance" have far less competition and more targeted traffic.

Mistake 3: Set-and-Forget Mentality

Keywords aren't permanent. Reader search behavior evolves. New competitors enter the market. Trending topics shift.

Review and update your backend keywords quarterly at minimum, monthly if you're actively promoting.

Mistake 4: Copying Competitors Exactly

Competitor research is for inspiration, not copying. If you target the exact same keywords as an established bestseller, you'll lose. Find gaps in their strategy and own those spaces.

Mistake 5: Using Keywords That Don't Match Your Book

Appearing for irrelevant searches gets clicks but kills conversions. Low conversion rates signal to Amazon that your book doesn't satisfy searchers, tanking your overall ranking.

Only target keywords that genuinely describe your book's content, themes, and audience.

How to Test If Your Keywords Are Working

After updating your backend keywords, verify they're having an impact.

Simple Keyword Verification

1. Open an incognito browser window
2. Go to Amazon.com
3. Search for one of your keywords in quotes (e.g., "cozy mystery bakery")
4. Look for your book in the results

If your book appears (even if not on page one), your keywords are indexed. If it doesn't appear at all, check for errors or keyword policy violations.

Track Ranking Changes

For systematic tracking, monitor your ranking position for target keywords over time:

• Note your starting position for each keyword
• Check weekly for movement
• Correlate rank changes with sales changes
• Adjust keywords that aren't performing

The Launch Fast Rank Tracker automates this process, showing week-over-week ranking trends and identifying which keywords correlate with sales.

Monitor Sales Impact

Ultimately, keyword success means more sales. Track:

• Total units sold (compare before/after keyword changes)
• Page reads (for Kindle Unlimited books)
• Traffic sources (if running Amazon Ads)

Give keyword changes 4 to 6 weeks before evaluating impact. Search ranking improvements take time.

FAQ: Amazon Backend Keywords for Books

How many keywords can I use per book?

Amazon KDP provides 7 keyword fields. Each field accepts approximately 50 characters (varies slightly by marketplace). Use all seven fields with complete phrases, not single words.

Do keywords affect print and ebook differently?

Keywords work the same way for ebooks, paperbacks, and hardcovers. Keep your keywords consistent across all formats of the same book for maximum discoverability.

How long until keyword changes take effect?

Most changes reflect in search results within 24 to 72 hours. However, ranking improvements from new keywords can take weeks to materialize as Amazon's algorithm processes the changes.

Can I use competitor author names as keywords?

No. Using other authors' names, book titles, or brand names you don't own violates Amazon's Terms of Service and can result in your book being suppressed or removed.

Should keywords be different from my title?

Yes. Don't waste backend keyword space repeating words from your title. Amazon already indexes your title. Use backend keywords for terms that would look awkward in your title but are still relevant searches.

Do backend keywords work for Kindle Unlimited?

Absolutely. Backend keywords help your book appear in search results regardless of whether readers purchase outright or read through KU. More visibility means more page reads.

How often should I update my keywords?

Review keywords monthly for actively promoted books, quarterly for backlist titles. Always update before major promotions or seasonal opportunities.

Start Optimizing Your Book's Discoverability Today

Backend keywords are one of the highest-leverage activities for self-published authors. A few hours of research and optimization can generate ongoing organic traffic for years.

Here's your action plan:

1. Audit your current keywords (or add them if you haven't yet)
2. Research 20 to 30 potential keywords using the methods in this guide
3. Select the 7 best phrases based on search volume, relevance, and competition
4. Update your KDP listing with your new keywords
5. Track your ranking for target keywords over the next 4 to 6 weeks
6. Iterate and improve based on performance data

Ready to take your Amazon keyword research to the next level?

Sign up for Launch Fast and get access to professional-grade keyword research tools:

• PPC Insights: Analyze competitor keyword strategies
• Gap Analysis: Find keyword opportunities your competitors are missing
• Rank Tracker: Monitor your organic ranking week over week
• Keyword Research Suite: Discover high-volume, low-competition keywords

The same tools that help FBA sellers dominate product categories work just as well for authors. Because at the end of the day, Amazon's search algorithm doesn't care whether you're selling garlic presses or gothic romances. It cares about relevance, keywords, and conversion.

Make your book discoverable. The readers are searching. Let Amazon help them find you.