KDP Formatting Requirements: Avoid Rejection

Amazon rejects or quality-flags roughly 8-12% of first-time KDP uploads due to formatting issues. The most common causes aren't typos or bad writing, they're technical problems with file structure, cover dimensions, and accessibility compliance that are entirely preventable. Here's every formatting specification KDP requires, what triggers rejections, and how to get your upload right the first time.

Ebook File Format Requirements

KDP accepts four ebook file formats, but they're not equally reliable.

Recommended: EPUB 3.0

EPUB is the industry-standard ebook format, and EPUB 3.0 is the version Amazon recommends as of 2026. Key advantages:

• Full control over formatting, fonts, and layout
• Native accessibility support (metadata, alt text, semantic structure)
• Validated by industry tools (epubcheck, DAISY Ace) before upload
• Reflowable content that adapts to any screen size

Amazon converts EPUB files to its proprietary KF8/AZW3 format internally. The conversion is generally faithful, but you should always preview your book using Kindle Previewer 3 (free from Amazon) before publishing.

Acceptable: DOCX

Microsoft Word files work but give you less control. Amazon's conversion engine interprets Word formatting, and the results are sometimes unpredictable:

• Tables of contents generated via Word's built-in TOC feature usually convert correctly
• Manual TOCs (typed text with no hyperlinks) often break
• Heading styles must use Word's built-in Heading 1, Heading 2, etc.
• Images should be inserted inline, not floating or anchored
• Embedded fonts may not transfer

Acceptable: KPF (Kindle Package Format)

Created exclusively with Amazon's Kindle Create tool. Good for:

• Print replica books (fixed layout matching your print edition)
• Books with complex layouts (cookbooks, children's books)
• Authors who want a visual, drag-and-drop formatting tool

Limitations: KPF is proprietary and cannot be distributed on other platforms.

Deprecated: MOBI

Amazon stopped accepting MOBI uploads in 2023. If you have existing MOBI files, convert them to EPUB 3.0 before uploading.

Format Comparison

Ebook Interior Formatting Rules

Heading Structure

Amazon's quality system checks your heading hierarchy. Valid heading structure means:

• Start with H1 (usually your chapter titles)
• Don't skip levels, H1 followed by H3 (missing H2) triggers a quality warning
• Use heading tags semantically, not for visual styling
• Every chapter should have at least one heading

Invalid heading structure is one of the top causes of Amazon quality suppression. A single skipped heading level (like H2 jumping to H4) can flag your entire book.

Table of Contents

KDP requires a functional, hyperlinked table of contents. Two types exist:

HTML/NCX TOC (required), An internal navigation structure embedded in the EPUB file. This is what powers the "Go to" menu on Kindle devices. Without it, Amazon will reject your upload.

Inline TOC (recommended), A visible table of contents page at the beginning of your book that readers can see in the Look Inside preview. While not strictly required, Amazon strongly recommends it and readers expect it.

Images

• Format: JPEG or PNG (JPEG preferred for photographs, PNG for diagrams/text)
• Resolution: At least 300 DPI for print, 72-150 DPI for ebook (higher DPI increases file size and delivery fees)
• Maximum file size: 50MB per image for print, no hard limit for ebook but total EPUB should stay under 650MB
• Color space: RGB for ebook, CMYK for print interiors
• Alt text: Required for accessibility compliance, every <img> tag should have a descriptive alt attribute

Missing alt text on images is a leading cause of accessibility quality flags. Our guide to alt text in ebooks explains how to write effective descriptions.

Fonts

• KDP supports embedded OTF and TTF fonts in EPUB files
• You must have licensing rights for any fonts you embed
• Amazon's default font (Bookerly) is used when no font is embedded or when readers override with their preferred font
• Don't embed more than 3-4 fonts, each font increases file size and delivery fee

Links

• All internal links (TOC, footnotes, cross-references) must work correctly
• External links must use https:// (not http://)
• Link text must have sufficient color contrast against the background, at least 4.5:1 ratio per WCAG 2.1 AA standards
• Links that are indistinguishable from body text trigger accessibility quality warnings

Ebook Cover Requirements

Your ebook cover is the single most important marketing asset. Amazon has specific technical requirements:

Common Cover Rejection Causes

• Dimensions below 1,000 x 625 pixels
• Aspect ratio significantly different from 1.6:1 (resulting in white bars)
• Blurry or pixelated images
• Text that is illegible at thumbnail size
• References to pricing, promotions, or "bestseller" claims on the cover
• QR codes on the cover
• Images that don't represent the book's content

Print Formatting Requirements

Interior PDF

Print interiors must be submitted as a single PDF file with specific technical requirements:

Gutter Margins

The gutter (inside margin) needs to increase with page count because thicker books don't open as flat:

Print Cover

Print covers wrap around the entire book, front, spine, and back. Amazon provides a cover template calculator that generates a PNG template based on your exact specifications.

Key dimensions:

• Front cover: Match your trim size exactly
• Spine width: Calculated from page count and paper type (white paper: page count x 0.002252", cream paper: page count x 0.0025")
• Back cover: Same dimensions as front
• Bleed: 0.125" beyond the trim line on all edges
• Barcode area: Amazon places a barcode on the back cover, leave a 2" x 1.2" white rectangle in the bottom-right corner

Accessibility Requirements

This is the area most authors overlook and the one Amazon has been enforcing most aggressively since 2024. Accessibility compliance affects both acceptance and ongoing visibility.

What Amazon Checks

Amazon's quality system evaluates your EPUB against accessibility standards that align with WCAG 2.1 Level AA:

How to Pass Accessibility Checks

The fastest path to compliance:

1. Format your book as EPUB 3.0 with proper semantic markup
2. Use heading tags correctly, H1 for chapters, H2 for sections, H3 for subsections, never skip levels
3. Add alt text to every image, describe what the image shows in 125 characters or less
4. Include accessibility metadata in your content.opf file
5. Ensure link contrast, hyperlinks should be visually distinguishable (blue with underline is safe)
6. Validate before uploading, run your EPUB through an accessibility checker

Our comprehensive ebook formatting guide covers the broader formatting landscape, and our EPUB accessibility guide goes deep on the accessibility layer specifically.

Common Rejection Reasons and Fixes

1. "Content quality issue detected"

Cause: Usually accessibility-related, broken headings, missing alt text, or absent metadata. Fix: Run your EPUB through an accessibility scanner and fix all violations.

2. "Cover image doesn't meet requirements"

Cause: Dimensions too small, wrong aspect ratio, or content violations. Fix: Use a 2,560 x 1,600 pixel canvas in RGB color space. Remove any pricing, promotional text, or "bestseller" claims from the cover.

3. "Table of contents is missing or broken"

Cause: No NCX/NAV document in the EPUB, or hyperlinks in the TOC point to wrong destinations. Fix: Rebuild your TOC using your EPUB editor's built-in TOC generator. Verify every link works.

4. "Spell check indicates possible errors"

Cause: Amazon's automated spell checker flagged unusual words, names, or technical terms. Fix: This is usually a false positive. Review the flagged words, and if they're intentional (character names, made-up words, technical jargon), you can proceed. Add a note in the description if needed.

5. "Interior file doesn't match trim size"

Cause: Your PDF page dimensions don't match the trim size you selected in KDP. Fix: Ensure your PDF is exported at exactly the trim size you chose (e.g., 6" x 9" for a 6" x 9" book). Include bleed if you selected bleed-enabled.

Pre-Upload Checklist

Before clicking "Publish" on KDP, verify:

• EPUB validates with epubcheck (0 errors)
• EPUB passes accessibility checks (no critical violations)
• All heading levels are sequential (H1 > H2 > H3, no gaps)
• Every image has alt text
• Table of contents is hyperlinked and functional
• Cover meets dimension requirements (2,560 x 1,600 preferred)
• Previewed in Kindle Previewer 3 on phone, tablet, and e-reader views
• Front matter is minimal (copyright, title page, save dedications and acknowledgments for the back)
• Back matter includes links to your other books
• File size is reasonable (under 50MB for most ebooks)

For the complete KDP strategy beyond formatting, see our Amazon KDP Complete Guide.

Frequently Asked Questions

What file format is best for KDP ebooks?

EPUB 3.0 is the best format for KDP ebook uploads. It gives you full control over formatting, supports accessibility metadata natively, and can be validated before upload. DOCX works for simple novels but introduces conversion unpredictability. KPF is only necessary for fixed-layout books.

Can Amazon reject my book for accessibility issues?

Amazon rarely rejects books outright for accessibility issues, instead, it applies quality flags that reduce your visibility in search and recommendations. However, books with no table of contents or severely broken formatting can be rejected during review. The practical effect of a quality flag is similar to rejection: your book is technically available but effectively invisible.

How do I fix heading hierarchy in my EPUB?

Open your EPUB in an editor like Sigil or Calibre. Search for heading tags (h1, h2, h3, etc.) and ensure they follow sequential order. If chapter titles use H1, section titles should use H2, and subsections should use H3. Never skip from H1 to H3 or H2 to H4. If you're not comfortable editing EPUB code manually, accessibility tools like Rahatt can auto-fix heading hierarchy issues.

What happens if my cover is the wrong size?

If your cover dimensions are above the minimum (1,000 x 625) but not the ideal ratio, Amazon will auto-resize it, which may add white bars or crop your image. If it's below the minimum, your upload will be rejected. Always design at 2,560 x 1,600 pixels and you'll never have issues.

Do I need to format differently for Kindle Unlimited vs. regular sales?

No. The same EPUB file is used whether a reader purchases your book or reads it through Kindle Unlimited. However, KU readers' pages are counted using KENPC (Kindle Edition Normalized Page Count), which normalizes for formatting differences. Artificially inflating page count through large fonts or excessive spacing violates KDP's terms and risks account termination.