Understanding the Amazon KDP algorithm in 2026 is no longer optional if you want your book to surface in search. The platform has changed significantly — Rufus AI has reshaped how Amazon interprets metadata, mobile now dominates purchases, and the royalty structure shifted in mid-2025. If you published two years ago and haven't revisited your listing strategy, a lot of what you knew is out of date. This guide covers what actually drives visibility and sales right now.
How the A10 Algorithm Works
Amazon's ranking algorithm — commonly called A10 — rewards books that convert browsers into buyers, not just books with stuffed keywords. The core signals it weighs are sales velocity, conversion rate, keyword relevance, external traffic, and reviews.
The signal that surprises most authors is external traffic. Sales driven from outside Amazon — your email list, social media, a blog post — are reported to influence organic ranking approximately 3x more than sales generated through Amazon's own internal ads. That means building any kind of off-platform audience has a direct ranking payoff, not just a revenue one.
Conversion rate is the other lever most authors underweight. A healthy eBook conversion rate on Amazon is 3–10%. If yours is below 2%, the algorithm reads that as a signal that your cover or pricing is putting people off — and it will rank you accordingly. Reviews amplify everything: more reviews, higher average rating, and recent review activity all feed into how Amazon weighs your book's relevance and trustworthiness.
You can track how your book's BSR moves in response to these signals using the BSR Sales Calculator — useful for estimating whether a ranking change is translating into meaningful sales.
Royalty Rates in 2026
The royalty structure matters for pricing strategy, and 2025 brought a meaningful change to print royalties that many authors missed.
Kindle eBooks: The 70% royalty tier applies when you price between $2.99 and $9.99 in 41 eligible territories. Outside that range — or for sales in Brazil, India, Japan, and Mexico without KDP Select enrollment — the rate drops to 35%. On the 70% tier, Amazon charges a delivery fee of $0.15 per MB. No delivery fee applies on the 35% tier. Fiction eBooks tend to perform well in the $3.99–$5.99 range, which keeps you firmly in the 70% band while staying competitive.
Print books (post June 10, 2025): Amazon changed the paperback royalty structure. Books priced at $9.98 USD or below now earn 50% of list price minus printing costs — down from 60%. Books priced $9.99 or above retain the 60% rate. Regional thresholds apply: UK £7.98, Canada $13.98 CAD, Australia $13.98 AUD. Amazon simultaneously reduced color printing costs from $0.0270 to $0.0255 per page, though this does not fully offset the royalty reduction for most titles. Expanded Distribution carries a 40% royalty.
The practical implication: if you're pricing paperbacks just under $9.99, it's worth running the numbers. The KDP Royalty Calculator makes it quick to compare net earnings across price points.
Keyword Strategy: The 7-Field, 500-Byte Rule
KDP gives you 7 keyword fields per listing. These are backend fields — readers never see them — but they determine which searches your book is eligible to appear in, so getting them right matters.
The byte limit per field is 500 bytes, though rollout has been inconsistent across regions. A conservative safe floor, especially for US, UK, and EU listings, is 249 bytes. Critically, this is a byte limit, not a character limit. Standard English letters count as 1 byte each. Special characters and emojis count as 2 or more bytes, so avoid them in keyword fields.
KDP's own guidance says single words outperform phrases for discoverability. Use your 7 fields to cover distinct search angles — think reader intent, sub-genre, comparable themes — rather than repeating terms you've already used in your title or subtitle.
Officially prohibited in keyword fields:
- Information already in your title, contributors, or categories
- Subjective quality claims (e.g., "best novel ever")
- Time-sensitive language ("new," "on sale," "available now")
- Generic terms like "book"
- Program names like "Kindle Unlimited" or "KDP Select"
- Misleading author names or unauthorized brand names
- Quotation marks or HTML tags
Keywords can be updated frequently without penalty, so test and iterate. See the KDP how-to guides for more on building a keyword strategy from scratch.
Cover and Metadata Specs
Mobile drives roughly 82% of Amazon purchases, and on mobile, your cover and title are doing almost all the work. Only around 60 characters of your title are visible before it gets cut off on a mobile listing — so front-load the most important information.
eBook cover requirements:
- Ideal dimensions: 2,560 x 1,600 px (height x width)
- Minimum: 1,000 x 625 px | Maximum: 10,000 px in either dimension
- Aspect ratio: 1.6:1 (height to width)
- File formats: TIFF (.tif/.tiff) or JPEG (.jpeg/.jpg) only
- Max file size: 50 MB
- Color profile: RGB — not CMYK
These aren't suggestions. Submitting a CMYK cover or wrong dimensions can result in rejection or a low-quality render that hurts conversions before a single reader clicks through.
File Format Requirements
KDP accepts several eBook formats: DOCX, KPF (via Kindle Create), EPUB, HTML, RTF, TXT, and PDF. PDF is supported for English and eight other languages (French, German, Italian, Portuguese, Spanish, Catalan, Galician, and Basque). For everything else, use EPUB or KPF.
One important change: as of March 2025, Amazon no longer accepts MOBI files for fixed-layout eBooks. If you have any fixed-layout titles — children's books, illustrated non-fiction, cookbooks — check your format before uploading a new version.
For print books, PDFs must include a 0.125-inch bleed on all edges. KDP also limits new title creation to 10 titles per book format per week, so if you're publishing in volume, plan your upload schedule accordingly.
Driving External Traffic
Given that external sales carry approximately 3x the ranking weight of internal ad sales, building a traffic source outside Amazon is one of the highest-leverage things you can do for organic rank.
Amazon's Attribution program makes this even more attractive: it offers a Brand Referral Bonus of approximately 10% cash back on referral fees for sales driven from external traffic. That's a meaningful offset for the effort of running external campaigns.
The practical playbook here isn't complicated — a newsletter, a consistent social presence, or content marketing that sends readers to your Amazon listing all count. The key is using Amazon Attribution links so those external sales get credited correctly and you receive the referral bonus.
A+ Content and Rufus AI
A+ content — the enhanced product description with images, comparison charts, and branded modules — is reported to lift conversion rates by 5–10%. Given that conversion rate is one of the primary ranking signals, that's a meaningful gain for something you set up once. If you're not using A+ content yet, it's a straightforward win.
Rufus — Amazon's AI shopping assistant — is now part of how your book surfaces in search. Unlike traditional keyword matching, Rufus performs semantic and contextual analysis, scanning your reviews, themes, and metadata to understand what your book is about and who it's for. This means stuffing keywords that don't reflect your book's actual content is increasingly counterproductive. Your description, editorial reviews, and even the language readers use in reviews all feed into how Rufus categorises your book.
If you want to see how your niche stacks up before you publish, the KDP niche pages give you a research starting point by category.
Pubscout: See Live Data on Any Book Page
The Pubscout Chrome Extension overlays live BSR, estimated monthly sales, and niche data directly on any Amazon book listing. If you're doing competitive research or validating a niche, it saves a significant amount of manual work — the data is right there as you browse.
AI Disclosure Rules
Amazon now requires authors to declare whether their book contains AI-generated content. The distinction matters: AI-generated means content produced by an AI tool with minimal human creative input; AI-assisted means a human used AI tools but made the substantive creative decisions.
Disclosure is self-reported during the publishing process. Getting this wrong isn't just a compliance risk — as AI-disclosure data becomes more visible to readers, it's increasingly a trust and conversion issue. Be accurate about how your content was produced.
The KDP landscape in 2026 rewards authors who treat their listing as a product with ranking signals to manage — not a static page you set once and forget. Cover quality, pricing strategy, keyword hygiene, and external traffic all compound over time. Start with whichever lever your current listing is weakest on, and revisit the others systematically.