Understanding how Amazon’s search algorithm works is crucial for your success as a self-published author. When readers search for books, Amazon’s system analyses both categories and keywords to determine which books to show and in what order. Think of it as a sophisticated matchmaking system between your book and potential readers.
This guide will show you how to leverage Amazon’s discovery systems through strategic use of keywords and categories, maximising your book’s visibility.
The fundamentals of Amazon’s discovery system
Amazon uses a complex ranking algorithm that considers multiple factors, including your keywords, categories, and sales history.
Think of Amazon’s search system as a librarian who needs to match readers with their perfect next book. This librarian (the algorithm) looks at three main elements: your keywords, your categories, and how well your book has performed with similar readers. Just as a skilled librarian learns which books to recommend to which readers, Amazon’s algorithm learns from user behaviour to refine its recommendations.
Although Amazon’s exact algorithm is a closely-guarded secret, we know it weighs factors in your book’s metadata (all the information about your book) differently. Your title carries the most weight, followed by your subtitle, then your categories, and finally your keywords. Understanding this hierarchy helps you prioritise where to place your most important search terms.
Mastering Keywords
Your seven keyword boxes are like seven opportunities to tell Amazon’s librarian about your book. Each box allows 50 characters, and here’s the clever part: Amazon’s algorithm creates combinations of words within each box. For example, if you write “Victorian London romance scandal nobility,” Amazon might match your book with searches for:
- Victorian romance
- London scandal
- Victorian nobility romance
This multiplication effect means you can achieve hundreds of search combinations with just seven carefully crafted keyword boxes.
Strategic keyword placement
Instead of spreading your keywords randomly, use this three-tier strategy:
- Tier 1 (Boxes 1-3): Your power keywords
These should be your most specific, targeted phrases. For a Victorian romance, you might use:- Box 1: “Victorian London romance scandal nobility”
- Box 2: “historical love story class difference”
- Box 3: “forbidden romance nineteenth century”
- Tier 2 (Boxes 4-5): Your genre elements
Focus on specific elements that readers search for:- Box 4: “strong heroine arranged marriage duke”
- Box 5: “sweet clean traditional courtship”
- Tier 3 (Boxes 6-7): Your emotional promises
These connect with reader desires:- Box 6: “happily ever after feel good romance”
- Box 7: “emotional historical love story”
Monitor keywords that generate sales
Here’s a lesser-known technique: Amazon’s algorithm gives more weight to keywords that generate actual sales. Monitor which search terms are bringing you sales (visible in your Amazon advertising dashboard if you run ads) and incorporate these proven converting terms into your keyword strategy.
KDP categories
Think of Amazon’s category system as a vast library with countless shelves. While you initially get to choose three main shelves (categories) for your book, there’s actually an extensive network of additional shelving spaces where your book could potentially sit. Understanding how to navigate this system can dramatically increase your book’s chances of being discovered by the right readers.
Primary Category Selection
Your initial three categories serve as your book’s primary homes on Amazon. When choosing these, consider both visibility and relevance. A category might seem perfect for your book, but if it’s oversaturated with thousands of titles, your book might get lost in the crowd. Conversely, a less competitive category might offer better visibility but could put your book in front of the wrong readers.
For example, if you’ve written a romance novel set in Victorian London featuring a medical theme, you might consider these category combinations:
- Romance > Historical Romance > Victorian Historical Romance
- Romance > Medical Romance
- Literature & Fiction > Literary Fiction > Historical
This combination provides a mix of broad appeal (‘Historical Romance’ and ‘Literary Fiction’) and a specific niche (‘Medical Fiction’) where your book might face less competition.
Advanced category selection strategy
Here’s a powerful approach many authors overlook: Some categories have much lower competition than others, yet they attract the same readers. For instance, a romance book might face fierce competition in “Contemporary Romance” but could rank much higher in “Small Town & Rural Fiction” while reaching similar readers.
You can actually appear in more than three categories by using specific keyword triggers. For example, including “clean sweet romance” in your keywords might automatically place your book in the “Clean & Wholesome Romance” category, even if you haven’t directly selected it.
The Power of Hidden Categories
What many authors don’t realise is that Amazon’s category system is like an iceberg – what you see in KDP is only the tip. While you’re limited to selecting three categories during initial setup, Amazon actually maintains an extensive network of additional categories that can dramatically increase your book’s visibility.
These hidden categories can be particularly valuable for two reasons:
- Reduced Competition: These specialised categories often have fewer books competing for visibility. While your book might struggle to reach the top 100 in “Romance,” it could more easily achieve a high ranking in “Victorian Historical Romance”.
- Targeted Readership: Readers who browse specific categories tend to be more invested in those particular niches. Someone exploring “Victorian Historical Romance” is likely to be more interested in your specific story than someone casually browsing general romance categories.
Finding hidden categories
To uncover these hidden categories, study the success paths of similar books in your genre. Visit Amazon’s book store and examine the category listings of successful titles that share elements with your book. Look at their product details section – you’ll often discover categories that aren’t available in KDP’s standard selection.
Pay particular attention to:
- The full category paths (each level of categorisation)
- The number of books ranked in each category
- The sales ranks of top-performing books in these categories
Requesting category additions
Once you’ve identified promising hidden categories, you can request addition to them through Amazon’s KDP support. Here’s the process:
- Gather your category strings (the full path of each category)
- Visit KDP support through your dashboard
- Select “Amazon Store & Product Detail Page” followed by “Update Amazon Categories”
- Submit your request professionally, including your book’s ASIN and full category paths
Category expansion through keywords
Here’s a lesser-known technique: certain keywords can automatically place your book in additional categories. Incorporating specific keywords into your book’s metadata can influence its placement in additional categories on Amazon, even beyond the ones you directly select during the KDP setup. Amazon’s system uses these keywords to determine the most appropriate categories for your book, enhancing its discoverability.
How It Works:
- Keyword Influence on Categories: By including particular keywords that align with certain genres or themes, Amazon may automatically assign your book to relevant categories. For example, adding “clean sweet romance” to your keyword list can place your book in the “Clean & Wholesome Romance” category, even if you didn’t manually select it.
- Research Keywords: Investigate which keywords are associated with your desired categories – check competitor books.
- Monitor Category Placement: After updating your keywords, check your book’s detail page to see which categories it’s listed under. Adjust your keywords as needed to ensure your book appears in the most relevant categories.
By strategically selecting your keywords, you can enhance your book’s visibility across multiple categories, potentially reaching a broader audience and increasing sales.
Unavailable categories
Frustratingly, some Amazon categories aren’t available for all book formats, like eBooks versus paperbacks. The categories also vary between different marketplaces, such as Amazon.com and Amazon.co.jp. When you’re choosing categories, concentrate on your main marketplace.
Creating your category strategy
The most effective approach combines standard and hidden categories with keyword-triggered categories. Here’s how to develop your strategy:
- Select your initial three categories based on:
- Relevance to your book
- Competition level
- Potential for visibility
- Research hidden categories by:
- Analysing similar successful books
- Noting categories with moderate competition
- Identifying specific niches where your book fits perfectly
- Keyword-Triggered Categories: Finally, incorporate category-triggering keywords into your metadata by:
- Researching which keywords trigger category placement
- Including these terms naturally in your book’s metadata
- Monitoring which categories you gain access to
- Monitor performance across all categories by:
- Tracking your ranking in each category
- Noting which categories generate actual sales
- Adjusting your strategy based on performance data
By combining strategic use of both standard and hidden categories with effective keyword optimisation, you create multiple pathways for readers to discover your book.
Implementation and monitoring strategy
Develop a systematic approach to testing different keywords:
- Record your initial keyword selections
- Monitor your Amazon sales rank for two weeks
- Change one keyword box at a time
- Track any changes in visibility and sales
- Keep the better-performing keywords and continue testing
Similarly, monitor your category performance:
- Record your Amazon bestseller rank in each category
- Calculate how many sales you need to reach the top 100
- If a category proves too competitive, consider switching to a related but less competitive one
- Look for categories where books similar to yours are performing well
Long-term visibility
The key to maintaining strong visibility on Amazon is understanding that optimisation isn’t a one-time task. Amazon’s algorithm continuously evolves, and reader search patterns change over time. Consider setting a quarterly schedule to review and update your keywords and categories based on performance data.
Remember that seasonal trends can significantly impact search patterns. For instance, romance readers might search for “beach romance” in summer and “Christmas romance” in winter. Plan your keyword updates accordingly.
Final thoughts
Success on Amazon requires thinking like both a marketer and a reader. Consider creating a spreadsheet to track which keywords and categories perform best for your books. This data becomes invaluable as you publish more titles and can inform your future marketing strategies.
Remember that Amazon’s algorithm favours relevancy above all else. The most successful authors maintain a balance between optimisation and authenticity, ensuring their keywords and categories accurately represent their books while maximising visibility to the right readers.
By implementing these strategies systematically and monitoring their effectiveness, you can significantly improve your book’s discoverability on Amazon, leading to improved sales and reader growth over time.