Epub Validator and Checker tool For Publishers

Free EPUB Validator & Checker Tool | Validate Your Ebook Online
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✦ 100% Free · No Sign-up · Instant Results

EPUB Validator
& Checker Tool

Upload your EPUB file for a complete validation report — metadata, structure, accessibility, compatibility, and more. Works for EPUB 2 & EPUB 3.

📚 50+ Checks run
⚡ Instant Results
🔒 Private — runs in browser
📱 Mobile Friendly
📖

Drop Your EPUB File Here

Drag & drop your .epub file, or click the button below

Supports EPUB 2.0.1 and EPUB 3.x · Max 100MB · 100% Private, runs in browser

⚙️ Parsing file…
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📘 EPUB Version: Detecting…
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What Is an EPUB Validator?

An EPUB validator is a tool that checks your ebook file against the official EPUB specification published by the W3C (World Wide Web Consortium). EPUB — which stands for Electronic Publication — is the most widely adopted open standard for ebooks. Both EPUB 2 and EPUB 3 have strict structural requirements, and any deviation from them can cause your book to render incorrectly or even refuse to open on certain devices.

Our free online EPUB validator and checker analyses your file directly in the browser — nothing is uploaded to a server, so your manuscript stays completely private. You get an instant, detailed report covering metadata completeness, file structure integrity, accessibility features, and compatibility with major e-readers.

What Does Our EPUB Checker Validate?

📋 Metadata

Checks for required OPF metadata: title, author/creator, language, identifier (ISBN/UUID), publication date, publisher, rights, and more.

🗂 File Structure

Validates the mimetype file, META-INF/container.xml, OPF package document, NCX/NAV navigation, and all spine/manifest references.

♿ Accessibility

Checks for alt text on images, language declarations, reading order, landmarks, headings hierarchy, and ARIA roles per WCAG and EPUB Accessibility 1.1.

📱 Compatibility

Reports compatibility with Kindle (KFX/MOBI), Apple Books, Kobo, Google Play Books, Adobe Digital Editions, and major reading apps.

🔗 Link Integrity

Detects broken internal links, missing manifest items, orphaned files not listed in the spine, and incorrect media types.

🎨 CSS & HTML

Validates XHTML content documents, checks for proprietary CSS, inline styles, external resource references, and font embedding.

How to Use the EPUB Validator

  1. Click “Choose EPUB File” or drag and drop your .epub file into the upload zone above.
  2. The tool will instantly parse and validate your file — no upload, 100% private.
  3. Review your Validation Score and the detailed breakdown across all tabs.
  4. Read the fix suggestions next to each issue to resolve problems.
  5. Download the full PDF/text report to share with your formatter or developer.

Frequently Asked Questions

Is this EPUB validator free? +
Yes, completely free with no sign-up, no account, and no file size limits (up to 100MB). The tool runs entirely in your browser using JavaScript — your EPUB file is never sent to any server.
Does it support EPUB 3 and EPUB 2? +
Yes. The validator detects your EPUB version automatically and applies the appropriate ruleset. EPUB 2.0.1 (with NCX navigation) and EPUB 3.0, 3.1, 3.2, and 3.3 (with NAV document) are all supported.
Will my EPUB pass Amazon KDP or Apple Books validation? +
Our compatibility tab gives you a platform-by-platform breakdown. Amazon KDP runs additional checks (especially around media types and JavaScript), while Apple Books requires valid EPUB 3 with specific metadata. Fixing all Errors and Warnings in our report will significantly improve your chances of passing platform reviews.
What is a good EPUB validation score? +
A score of 90–100 (Grade A) is ideal and means your EPUB will work correctly on virtually all e-readers. Scores of 70–89 (Grade B) indicate minor warnings that should be addressed. Below 70 means there are structural errors that may cause rendering issues or rejection by platforms like KDP or Kobo.
What causes EPUB validation errors? +
Common causes include: missing or malformed OPF metadata (no title, no identifier), missing container.xml, broken spine references, incorrect media types in the manifest, missing NCX/NAV navigation document, images referenced in HTML but not declared in the manifest, and non-XHTML-compliant content documents.
How do I fix EPUB validation errors? +
Each issue in our report includes a “How to fix” suggestion. For structural issues, you’ll need to unzip the EPUB (it’s a ZIP file), edit the XML/HTML files, and re-zip. Tools like Sigil (free, open-source EPUB editor), Calibre, or a code editor can help. Alternatively, hire a professional ebook formatter.
Is my ebook file private? +
Absolutely. This tool uses the browser’s built-in File API and JSZip library. Your EPUB is read locally by your browser — it is never uploaded to any server, and we don’t store any data from your file. Even your book’s content stays on your device.
What’s the difference between EPUB 2 and EPUB 3? +
EPUB 2 (released 2007) uses NCX navigation and supports basic HTML and CSS. EPUB 3 (current standard) adds HTML5, CSS3, JavaScript, MathML, SVG, audio/video, and a new NAV document for navigation. EPUB 3 is required for fixed-layout books (children’s books, textbooks, comics) and enhanced ebooks with media overlays.

Why Use Our EPUB Validator?

  • No installation needed — works in any modern browser on Windows, macOS, iOS, and Android.
  • 50+ automated checks covering the full EPUB 2 and EPUB 3 specification.
  • Actionable fix suggestions for every error and warning found.
  • Platform compatibility report for Amazon Kindle, Apple Books, Kobo, Google Play Books, and more.
  • Accessibility audit aligned with EPUB Accessibility 1.1 and WCAG 2.1.
  • Downloadable report you can share with your formatter, publisher, or developer.
  • Completely private — your manuscript never leaves your device.
  • Works on mobile — fully responsive design for iOS and Android.

© 2025 EPUB Validator Tool · Free Online EPUB Checker · Built for authors, publishers & developers

If you need it, explain your requirments in the extra information box below
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