EPUB Validator
Validate your EPUB files instantly. Check for structural errors, metadata compliance, and accessibility issues before publishing your ebook.
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Your files are securely uploaded for validation and automatically deleted after processing.
Why Validate Your EPUB Files?
Publishing an ebook is an exciting milestone, but nothing derails the process faster than having your file rejected by a major retailer. Apple Books, Amazon Kindle Direct Publishing, Google Play Books, and Kobo all have strict requirements for EPUB file quality. A single structural error can prevent your book from reaching readers.
EPUB validation ensures your ebook meets the official W3C EPUB 3.0 and 3.2 specifications. These standards guarantee that your book will display correctly across thousands of different devices and reading applications. From dedicated e-readers to tablets and smartphones, validated EPUBs provide a consistent reading experience.
Avoid Platform Rejections
Major ebook retailers automatically scan uploads for compliance issues. Catch and fix errors before submission to save time and frustration.
Ensure Reader Compatibility
Validated EPUBs work reliably on all devices, preventing broken layouts, missing images, or navigation problems for your readers.
Meet Accessibility Standards
Validation includes accessibility checks, helping ensure your ebook can be enjoyed by readers using assistive technologies.
Professional Quality
A validated EPUB reflects the care you put into your writing. Present your work with the technical quality it deserves.
How Our Tool Works
Validating your EPUB file takes just seconds. Our straightforward process gets you actionable results fast.
Upload Your File
Drag and drop your EPUB file into our validator or click to browse. Files up to 100MB are supported.
Instant Validation
Click the Validate button and our engine checks your EPUB against W3C standards. We examine structure, metadata, navigation, content files, and accessibility in seconds.
Review Results
See a detailed log of validation checks, including any errors or warnings. Each issue includes a clear explanation to help you understand and fix problems quickly.
Common EPUB Errors and How to Fix Them
Understanding common EPUB issues helps you create better ebooks. Here are the most frequent problems our validator catches.
Missing or Incomplete Metadata
Every EPUB must include a title, unique identifier, and language code in the package document (content.opf). Missing metadata is one of the most common reasons for retailer rejection. Ensure your EPUB authoring tool properly fills in all required fields.
Broken Image References
Images must be correctly referenced in both the manifest and content files. Common issues include wrong file paths, missing images, or referencing files that were renamed. Always verify image paths after moving or reorganizing your project.
Invalid XHTML Content
EPUB content files must be well-formed XHTML. Unlike regular HTML, XHTML requires properly closed tags, lowercase element names, and quoted attributes. Use an XML validator or your EPUB editor's built-in checks to catch syntax errors.
NCX Navigation Deprecation
The NCX navigation format is from EPUB 2 and is deprecated in EPUB 3. While many reading systems still support it, you should include a modern EPUB 3 navigation document (nav.xhtml) as the primary navigation. Some tools include both for maximum compatibility.
CSS Compatibility Issues
Not all CSS properties are supported across e-readers. Complex layouts, certain fonts, and advanced CSS features may not render correctly. Stick to well-supported properties and test your EPUB on multiple devices when using custom styling.
Missing Alt Text for Images
Accessibility guidelines require all meaningful images to have alternative text descriptions. This helps visually impaired readers using screen readers understand your content. Decorative images can use empty alt attributes (alt="").