Free checker
Validate Your EPUB Online — the Check the Stores Run
Drop in the .epub and get the epubcheck verdict Kindle and Apple Books will give it, plus a plain-English look inside: chapters in the navigation, landmarks, cover image, title, author and language.
KDP, Apple Books and Kobo run the W3C validator (epubcheck) on every EPUB you upload and refuse files with errors — a navigation document missing from the package, a landmark pointing outside the spine, a malformed XHTML file. The errors are precise and cryptic. This validator runs the same epubcheck (version 5.4) on your file and adds what the stores look at next: whether the navigation document lists your chapters, whether landmarks tell the reader where the book starts, whether a cover image is declared, whether the title, author and language are in the package. The file is read in memory and never stored.
Free, no account Seconds per file Nothing stored
Last updated: October 16, 2026 · Reviewed by the Ceeryo team
Free, no account. The file is read, reported on and forgotten.
Real output
What the typeset pages actually look like
Chapter opener and body page from each interior theme — rendered from the engine's real output at 6×9, not mockups.
How it works
From manuscript to book in four steps
The fastest way from a finished Word manuscript to print-ready files — no templates, no desktop app, no per-page fiddling.
- Step 1
Upload your manuscript
Drop in the .docx manuscript you have finished writing. Your file is processed only to typeset it and is never used to train models.
- Step 2
Chapters are detected
Chapter openings, scene breaks and italics are found automatically, without changing a word of your text.
- Step 3
The book is typeset
Trim size, margins and gutter, running heads, drop caps and chapter openers are set as a real book interior.
- Step 4
Download print PDF + EPUB
A print-ready interior PDF at your chosen trim size plus a clean EPUB, checked against the geometry KDP enforces.
In short
An EPUB passes a store's upload check when epubcheck reports no errors and the package carries a navigation document, landmarks, a declared cover, and a title, author and language. This free validator runs epubcheck 5.4 — the same check KDP and Apple Books run — and reports those facts in plain English, without storing the file.
What does epubcheck check?
That the EPUB is a correctly built package: the mimetype file first, a valid container and package document, every file listed in the manifest, every XHTML file well-formed, the navigation document present and its links valid, landmarks pointing at spine items, and metadata (identifier, title, language) present. Kindle and Apple Books run it at upload; a file with errors is refused before anyone sees the book.
The validator and a translation
Errors, then what they mean for readers
epubcheck says RSC-011 and a file path. The report under it says the thing an author needs: the chapter list has one entry for forty sections, there is no cover declared, the book will open on the copyright page because there are no landmarks. Every note is something a reader would notice.
- epubcheck 5.4 errors and warnings, as the stores see them
- Navigation entries counted against the sections in the spine
- Cover, landmarks, title, author and language checked in the package
- Pictures counted, the largest named — Kindle delivery costs rise with size
Features
Why authors choose Ceeryo
epubcheck 5.4
The W3C validator itself, not a lookalike — the same check KDP and Apple Books run at upload.
A look inside the package
Version, title, author, language, sections, navigation entries, landmarks, cover, pictures and size.
Nothing stored
The EPUB is read in memory, validated, reported on and forgotten. No account, no email.
Use cases
Where Ceeryo works best
KDP or Apple rejected the EPUB
See the exact errors and what they mean before trying again.
A converter's output
Calibre, Pandoc, Word's 'save as' — check what came out before readers do.
Before wide distribution
One validated file for Kindle, Apple Books, Kobo, Google Play and Draft2Digital.
Why not do it by hand?
Ceeryo vs. doing it manually
Typesetting a book by hand in Word or InDesign takes days and rarely passes KDP's checks the first time. Here's the difference.
Output quality
What the finished book files look like
Every run produces a preflight-checked print PDF and a clean EPUB — never a rewrite of your words. Here's what you get.
- Pass or fail from epubcheck 5.4, with every error listed
- Warnings separately — stores accept the file, you may still want to know
- Navigation, landmarks, cover and metadata in plain English
- Package facts: EPUB version, sections, pictures, size
Topic cluster
Related book formatting tools
Other ways to turn your Word manuscript into a finished book.
Word to EPUB for Publishing — Validated, With a Real Table of Contents
Not a file converter: an EPUB3 built from your chapters, with the navigation, landmarks and metadata Kindle, Apple Books and Kobo check at upload — and run through epubcheck before you download.
ebookformatterA Kindle Create alternative that doesn't lock you in
Free has a shape: Kindle Create's output works only on Amazon. If you want files you own — standard EPUB, print-grade PDF — that's the alternative.
ebookformatterVellum for Windows
Vellum doesn't run on Windows — and the usual answer is buying different desktop software. The browser needs no port.
formatterA Vellum alternative that runs in the browser
Vellum is excellent — and $249, Mac-only, and another app to learn. The alternative: upload the manuscript, download the book.
formatterAn Atticus alternative for finished manuscripts
Atticus wants to be where you write. If your book is already written in Word, you need a typesetter — not a second home for your text.
formatterCheck Your PDF for KDP Before You Upload It
Drop in the interior PDF and get KDP's own checks in seconds: trim size, page count, the inside margin your page count needs, the 0.25″ no-print zone, embedded fonts and picture resolution — with what to fix.
formatter
Frequently asked questions
Is this the same as the IDPF validator?+
The IDPF's online validator was retired; epubcheck is the W3C tool that replaced it and the one the stores run. This page runs epubcheck 5.4.
Does it fix the file?+
No — it reports. Fix the file in the program that made it, or upload the Word manuscript to Ceeryo and get a freshly built, validated EPUB.
Are warnings a problem?+
Stores accept files with warnings. They are listed separately so you can judge — a warning about a missing language or a large picture is worth a look; one about an unusual file name usually is not.
How big a file can I check?+
Up to 60 MB, read straight from your browser; the validator stops at that size. The file is never stored.
Need a clean EPUB instead?
Upload the Word manuscript and Ceeryo builds the EPUB — real chapters, navigation, landmarks, your cover — and runs this validator before you download.