Private EPUB validator online
Ebook validation guide
The EPUB formatting errors that fail validation.
Most rejected ebooks fail on a short list of structural errors. Spot them in your file before the store does.
Checked:
✓Missing or empty table of contents✓Images over file limits✓Broken manifest and spine entries
Private by default
Drop in the file you plan to publish
Choose a DOCX or EPUB. This first check runs in your browser; your manuscript is not uploaded.
The errors that appear most
Validators reject ebooks for missing navigation, invalid OPF metadata, files not declared in the manifest, and images that exceed store limits.
- Every asset must be listed in the manifest
- Cover image rules differ by store
- Inline styles that fight the reader fail
Checking your EPUB for free
Upload the file to the free EPUB validator. It inspects the package structure and reports the exact errors with fixes.
FAQ
Frequently asked questions
Why does my EPUB fail validation?
The three common causes are a missing TOC, assets absent from the manifest, and images over the store's size limit.
Can I fix an EPUB without rebuilding it?
Sometimes, but a clean rebuild from a well-styled DOCX is usually faster than patching the package.
Find every error before the store does.
Drop your EPUB into the free validator and get the full error list with fixes.