The Complete KDP Formatting Guide

Section 1KDP ebook formatting — what the process actually involves

Most authors expect to write a book, convert it to EPUB, and upload it. The actual process has more steps — and the ones that get skipped are the ones that cause rejections. KDP enforces structural rules that are invisible in Word or Google Docs but become critical once the file is converted and delivered to a reader.

The formatting workflow has four phases: prepare (clean the manuscript, build TOC and front/back matter), build (generate a valid EPUB file), validate (confirm the file passes structural checks), and publish (complete metadata, categories, and keyword fields before submitting). Skipping any phase means fixing problems after KDP or Apple Books rejects the file — which takes longer than getting it right before upload.

Section 2Manuscript formatting — cleaning up before you convert

Word and Google Docs store text in ways that break when converted to reflowable ebook formats. The problems are invisible in your editor but show up in the final EPUB: straight quotes instead of curly typographic quotes, double spaces after periods, Tab-based paragraph indentation that produces double-indentation on some Kindle devices, encoding artifacts (’ instead of an apostrophe), and stacked blank paragraphs used as visual spacing that EPUB converters interpret inconsistently.

Four rules fix the most common structural problems before conversion:

• Use paragraph styles for spacing — not blank lines between paragraphs or double Return presses. EPUB converters interpret stacked blank paragraphs as ghost spacing that creates inconsistent gaps across devices.
• Set first-line indentation in CSS — not with Tab or spacebar. Tab-indented paragraphs produce double-indentation on some Kindle models.
• Remove double spaces — visible in some EPUB readers and can trigger KDP's automated quality review.
• Avoid character-level formatting overrides — formatting applied via Ctrl+B is stored differently from style-based formatting and may not survive EPUB conversion cleanly on all devices.

The Word Manuscript Cleanup Checker scans your .docx for double spaces, straight quotes, stacked blank paragraphs, and stray formatting — free, no signup. For prose-level cleanup (dialogue punctuation errors, repeated words, clichés), the Manuscript Cleanup tool runs AI analysis on any length manuscript, with a free 500-word sample run available first.

Section 3EPUB — format overview and why KDP depends on it

EPUB (Electronic Publication) is the standard container format for reflowable ebooks — used natively by Apple Books, Kobo, and Google Play. KDP also uses it internally: even if you upload a Word document, KDP converts it to EPUB before converting again to its proprietary KFX format for delivery. Uploading a clean, correctly structured EPUB gives you control over what that intermediate file looks like, reducing conversion errors.

An EPUB file is a ZIP archive with a required internal structure:

• mimetype — must be the first file in the archive, stored uncompressed, containing exactly application/epub+zip.
• META-INF/container.xml — declares the path to the OPF package document. Without it, no reading system can open the file.
• OPF package document — lists every file in the EPUB (manifest) and the reading order (spine).
• nav.xhtml — the EPUB3 navigation document, containing the table of contents. Must appear in both the manifest and the spine.
• Chapter XHTML files — each chapter as a separate .xhtml file, declared in the manifest and ordered in the spine.

EPUB Formatter generates a valid EPUB 3.0 from pasted manuscript text — no Calibre, no Sigil, included in the Starter plan. Full Manuscript Mode accepts .docx or .txt uploads and runs formatting fixes before building the EPUB (free, no signup). After generating, run the free EPUB Validator to confirm all structural checks pass before uploading.

Section 4Kindle-specific formatting requirements

Kindle books are delivered in Amazon's KFX format. You never submit KFX directly — KDP converts your uploaded EPUB or Word document. What you control is how clean the source file is before conversion.

• Reflowable vs fixed layout. Reflowable lets text adapt to any screen size and font setting. Fixed layout locks the page design — useful for illustrated children's books but it breaks on small screens and large-text accessibility settings. For prose and most non-fiction, use reflowable.
• MOBI format is deprecated. Amazon stopped accepting .mobi uploads in 2022. Submit EPUB or Word.
• Enhanced Typesetting. Amazon applies improved hyphenation, kerning, and justification automatically on supported devices when your book meets its requirements. Books with clean EPUB CSS are more likely to qualify; heavy inline styles or image-based text typically disqualify the book. Amazon determines eligibility — there is no manual opt-in.
• Test with Kindle Previewer. Amazon's free Kindle Previewer simulates how your book renders across Kindle devices before upload. Run your EPUB through validation first, then test in Previewer — Previewer surfaces layout issues that validators don't catch (images, tables, drop cap rendering on older firmware).

The most common source of Kindle formatting problems is the Word export: straight quotes, double hyphens, double spaces, and encoding artifacts that render incorrectly after KDP's conversion. Kindle Format Fixer catches and corrects all eight common Word export issues in a single pass, included in the Starter plan.

Section 5Table of contents — KDP requirements and structure

A clickable, correctly structured Table of Contents is required for Kindle books. A missing or malformed TOC is one of the most consistent reasons books fail KDP quality review.

• EPUB3 nav.xhtml. The primary TOC lives in a navigation document marked with epub:type="toc" on the <nav> element. Each entry points to a chapter heading via a relative link inside the EPUB package.
• NCX fallback. Older Kindle devices rely on a toc.ncx file. Include both nav.xhtml and toc.ncx for backward compatibility. Omitting the NCX causes navigation to fail on older firmware.
• Spine position. KDP requires the TOC to appear in the EPUB spine before the first chapter — it must be a navigable location, not just a structural element declared in the manifest. A TOC in the manifest but absent from the spine can pass validation and still trigger KDP quality review.

TOC Generator outputs correctly structured Kindle HTML, EPUB3 nav.xhtml, and NCX XML from your chapter headings — paste your manuscript or just your headings, select output format, and copy the result. Included in the Starter plan.

Section 6Image formatting and resolution requirements

Images in Kindle ebooks have different requirements from print. Getting the format and color mode wrong is a common source of rejections that is easy to prevent.

• RGB, not CMYK. Ebook cover images and interior images must be in RGB color mode. CMYK images — typically prepared for offset print — produce washed-out or shifted colors in ebook readers. KDP does not convert color modes automatically.
• Format: JPEG or PNG. These are the only image formats supported inside EPUB packages. Images in EMF or WMF (often embedded by Word) will trigger validation errors. Save any affected images as PNG or JPG from the original source before converting.
• Resolution. Print images require 300 DPI at printed size. Ebook images render on screen, where 72–96 DPI is sufficient. High-resolution images increase file size without improving screen quality. Images prepared for print are safe to include in an ebook — they will not look worse, just add file size.
• Cover dimensions. KDP has specific minimum pixel requirements and a recommended aspect ratio for ebook cover images. Consult KDP's current cover image guidelines for exact values — these have been updated over time.
• Transparency. PNG supports transparency; JPEG does not. Transparent PNGs may render with a black or white background depending on the reader's theme. Test in Kindle Previewer before uploading, or flatten to a white background to avoid unpredictable rendering.

Cover Checker validates your ebook cover against KDP and Apple Books dimension and format requirements before you upload — free, no signup.

Section 7Font selection and embedding for ebooks

Font choice in ebooks is different from print. Most EPUB readers — including Kindle — let users switch to their preferred reading font at any time. Font selection matters most for the fallback when no user override is active, and for custom fonts you embed in the EPUB package.

• Safe system font stacks. If you do not embed a custom font, the device uses its built-in default. Declaring an explicit font-family stack makes the fallback intentional. Common stacks: Georgia, 'Times New Roman', serif for fiction body text; Helvetica, Arial, sans-serif for non-fiction with heavy structure.
• Serif vs sans-serif. Long-form prose traditionally uses a serif face — serifs assist horizontal tracking across lines on screen. Sans-serif works for shorter text, callouts, and non-fiction that reads in chunks. Pick one for body text and apply it consistently.
• Embedding custom fonts. A font embedded in the EPUB appears as “Publisher Font” in Kindle's font menu. Embedded fonts must be declared in the manifest and referenced via a CSS @font-face rule. Only embed fonts whose license permits EPUB redistribution — most commercial font licenses do not include it without a separate ebook license. Free fonts from Google Fonts generally permit embedding.
• Drop caps and chapter openers. Drop caps require ::first-letter with float: left and matching line-height. Not all readers render them identically — test in Kindle Previewer before using them as a visual anchor in every chapter.

CSS Snippet Generator outputs tested @font-face declarations, body-text stacks, drop cap styles, scene breaks, and blockquote formatting — each with a live preview, optimized for Kindle KFX and EPUB. Included in the Starter plan.

Section 8Chapter formatting — headings, scene breaks, and page breaks

Chapter formatting does not have a single required format — but it must be consistent across every chapter. Inconsistency is what readers and quality reviewers notice first.

• Consistent heading style. Use one heading style for every chapter opener — H1, H2, or a styled paragraph — and keep the format identical throughout. Mixing “Chapter One”, “Chapter 1”, and bare numerals across chapters breaks automated TOC generators and looks inconsistent in quality review.
• Scene breaks. The standard for marking a scene break within a chapter is three asterisks (***), a hash (#), or a decorative ornament. Plain blank lines are unreliable — EPUB converters often collapse them or flag them as ghost spacing. Whatever marker you choose, use it in every scene break in the book.
• Page breaks via CSS, not blank lines. Each new chapter should open on a fresh page via CSS (break-before: page), not by pressing Return multiple times. Stacked empty paragraphs collapse differently across devices and sometimes disappear entirely in conversion.
• First paragraph after a heading. Publishing convention is no indent on the first paragraph of a chapter (after the heading) and a first-line indent on all subsequent paragraphs. This is set in CSS (p.first { text-indent: 0; }), not by manually removing indentation in the document.

CSS Snippet Generator outputs page break rules, scene break styles, and drop cap CSS with live previews. Manuscript Cleanup flags inconsistent heading formats and stacked paragraph breaks before they reach the converter — 1 credit per run, free 500-word sample.

Section 9Metadata — what KDP requires and how to format it

Every EPUB package must include four required Dublin Core metadata fields in the OPF document. These are EPUB spec requirements — not just KDP requirements.

• dc:title — the book title, matching the title on the cover and in the KDP listing.
• dc:creator — the author name. Multiple dc:creator elements are allowed for co-authored works. In EPUB3, an opf:role attribute specifies the contributor relationship using MARC relator codes.
• dc:language — the primary language as a BCP 47 tag: en for English, en-US for American English, fr for French. This affects how reading systems handle hyphenation, text-to-speech, and search indexing.
• dc:identifier — a unique identifier, typically the ISBN. Must match the identifier referenced by the package element's unique-identifier attribute, or the EPUB fails spec validation.
• BISAC subject codes. BISAC codes classify books by genre and subject, and form the basis of KDP's category assignment. Adding dc:subject elements with BISAC codes and matching them to your KDP categories improves discoverability.
• 7 KDP keyword fields. Amazon gives you 7 keyword fields, each up to 50 characters. Use each slot as a complete phrase matching specific reader queries — not a list of single words.
• Book description. The description field on your KDP product page accepts HTML formatting — bold, italic, lists, and headings. For the character limit, supported tags, and a copywriting structure, see the KDP book description guide.

Metadata Builder fills all four required Dublin Core fields and generates formatted output for KDP, IngramSpark, Draft2Digital, and EPUB OPF — free, no account required. KDP Keyword & Category Finder generates 7 long-tail keyword phrases tailored to your genre and comparable titles, plus ghost category paths — 2 credits per run.

Section 10Validation — why it matters and what it checks

KDP's upload error messages are deliberately vague. A file can be rejected with “We found issues with your file” and no further detail. Running validation before submission tells you exactly what KDP's preprocessor will flag — container structure, required metadata, spine order, cover image declaration — so you can fix it before any store sees the file.

The three major stores have different strictness levels:

• KDP — accepts some structurally broken EPUBs and silently corrects or drops content. A file can upload successfully and still render incorrectly on Kindle devices.
• Apple Books — stricter: requires EPUB 3, rejects malformed XML, validates image quality and font embedding beyond what KDP checks. A file that uploads to KDP successfully can fail Apple Books submission.
• IngramSpark — sits between the two, with clearer rejection messages but stricter compliance requirements than KDP.

The free online EPUB Validator checks all 11 structural requirements — mimetype, container, OPF, metadata, spine, navigation, cover reference, image and CSS references, file size — in your browser, with plain-English error messages and fix links. Free, no signup. For deeper checks (ghost spacing, duplicate IDs, OPF manifest completeness, store-specific pass/fail reports for KDP, Apple Books, and Google Play), EPUB Validator Pro runs a full scan — 3 credits per run.

Section 11Common KDP formatting errors — and how to fix them

Most EPUB rejections come from the same six errors. Each links to a step-by-step fix guide.

• Missing manifest resource — A file exists in the EPUB archive but was never added to the OPF manifest, or a file declared in the manifest is absent from the archive. Usually caused by manual EPUB editing in Sigil or Calibre after the manifest was generated. Fix: open the OPF file, add or remove the corresponding <item> entry.
• Cover image not declared — The cover image is physically present but not linked with the correct manifest properties. KDP checks this specifically; missing declaration causes the cover to appear blank in the store listing. Fix: add properties="cover-image" to the cover image item (EPUB3), or <meta name="cover" content="cover-id" /> (EPUB2).
• Missing NCX navigation (toc.ncx) — The OPF references toc.ncx but the file is absent. Common with Scrivener and older Calibre exports that generate the OPF reference without creating the file. Fix: generate toc.ncx using the TOC Generator or rebuild it in Sigil via Tools → Table of Contents.
• Malformed XHTML (unclosed tag) — EPUB content files must be valid XML. An unclosed tag causes Apple Books and strict validators to reject the file outright. Fix: open the flagged content file, locate the unclosed tag at the reported line number, add the matching closing tag.
• EMF image without fallback — Word-to-EPUB conversions sometimes embed images in Windows-only EMF format. EPUB readers cannot display them and no fallback is provided, causing validation failure. Fix: re-save the image as PNG or JPG in the original Word document, replace it, and re-export.
• Duplicate ID — Two or more elements share the same id attribute. Causes navigation failures and Apple Books rejections. Fix: search the EPUB's HTML files for the duplicate id value and rename one occurrence to a unique string.

See the full EPUB errors directory →

Section 12Final KDP formatting checklist

Before uploading to KDP, Apple Books, or Kobo, confirm each item:

• Manuscript cleaned — no double spaces, straight quotes, Tab indents, or encoding artifacts — Word Manuscript Cleanup Checker (free)
• Prose consistency checked — dialogue punctuation, repeated words, style drift — Manuscript Cleanup (1 credit; free 500-word sample)
• EPUB file generated with correct mimetype, container.xml, OPF, and chapter structure — EPUB Formatter (Starter plan)
• Clickable Table of Contents present — nav.xhtml in manifest and spine, NCX fallback included — TOC Generator (Starter plan)
• Front matter complete — title page, copyright page, dedication — Front Matter Generator (Starter plan)
• Back matter complete — author bio, Also By, mailing list CTA — Back Matter Generator (3 credits)
• EPUB validates with zero structural errors — EPUB Validator (free)
• Cover image: JPEG or PNG, RGB color mode, dimensions meet KDP requirements — Cover Checker (free)
• Metadata complete: dc:title, dc:creator, dc:language, dc:identifier, BISAC category, 7 keywords — Metadata Builder (free)
• KDP keyword phrases: 7 complete phrases using all 50 characters, no banned terms — KDP Keyword & Category Finder (2 credits)
• File previewed in Kindle Previewer on at least one device size

What file format does KDP require for ebooks?

KDP accepts EPUB and Word (.docx) files. EPUB is the recommended format — it gives you full control over structure, styling, and metadata. KDP converts your upload internally to KFX for delivery. PDFs are not supported for reflowable ebooks. MOBI upload was discontinued in 2022.

Do I need to validate my EPUB before uploading to KDP?

Yes. KDP accepts many structurally broken EPUBs and silently fixes or drops content during conversion — meaning your book can look fine in your editor and still render incorrectly on Kindle devices. Apple Books and IngramSpark are stricter and reject malformed files outright. Validating before submission catches errors before any store sees the file.

How do I create a clickable Table of Contents for Kindle?

A Kindle-compatible TOC requires a nav.xhtml navigation document (EPUB3) and a toc.ncx file for older devices (EPUB2 fallback). Both must be declared in the OPF manifest and the nav must appear in the spine reading order. KDP will reject books where the TOC is declared only in the manifest but not in the spine.

What metadata is required for KDP EPUB uploads?

The EPUB spec requires dc:title, dc:creator, dc:language (as a BCP 47 tag such as "en"), and dc:identifier. KDP additionally requires a complete book description, BISAC category, and 7 keyword fields. Missing metadata fields can delay approval or reduce discoverability.

Why does my ebook look broken after converting from Word?

Word documents carry hidden formatting: straight quotes that convert inconsistently, double spaces, Tab-based indentation, encoding artifacts, and stacked blank paragraphs used for spacing. EPUB converters interpret these literally, producing visible errors in the final file. Running a cleanup pass before converting removes most of these.

What is the difference between EPUB Formatter and Full Manuscript Mode?

EPUB Formatter takes pasted text and generates a valid EPUB 3.0 — works for any source manuscript. Full Manuscript Mode accepts .docx or .txt file uploads, runs automatic formatting fixes before building the EPUB. If you are uploading from Word, Full Manuscript Mode handles both cleanup and EPUB generation in one step.

How do I fix common EPUB errors before uploading to KDP?

The most common fixable errors are: missing manifest resource (add the file to OPF manifest), cover image not declared (add properties="cover-image" in EPUB3), missing NCX navigation (regenerate toc.ncx), malformed XHTML (close the unclosed tag), and duplicate IDs (rename one occurrence). Run your EPUB through a validator first to identify which errors are present.

How do I format images for Kindle ebooks?

Interior images must be JPEG or PNG in RGB color mode. CMYK images produce washed-out colors on screen. KDP recompresses images during conversion to KFX, so start with the highest resolution available. For transparent PNGs, test in Kindle Previewer — some device themes render transparency as a black background.

Start with the free EPUB Validator — no signup, no Java, runs in your browser.