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Troubleshooting Book Upload Errors

Common errors when uploading books to BookAuth — file format issues, size limits, cover image problems, and how to fix them.

Updated April 10, 20261 views

If your book upload fails, this guide helps you diagnose and fix the most common issues.

File Upload Errors

"File format not supported"

Supported formats: ePub, PDF

  • Ensure your file extension is .epub or .pdf (not .docx, .mobi, .azw3)
  • If you have a Word document, convert to ePub using Calibre or Scrivener first

"File too large"

Maximum file size: 100 MB

  • Most eBooks are 1-10 MB. If your file exceeds 100 MB, check for embedded high-resolution images
  • Compress images within the ePub using Calibre
  • For PDFs, use Adobe Acrobat's "Optimize PDF" feature

"ePub validation failed"

Your ePub file has structural issues:

  • Run ePub through validation using epubcheck.org
  • Common issues:
    • Missing content.opf file
    • Invalid HTML inside chapters
    • Embedded fonts with licensing restrictions
  • Fix: use Calibre to "polish" the ePub or Sigil for manual editing

Upload Times Out

  • Check your internet connection
  • Try a wired connection instead of Wi-Fi
  • Compress the file and try again
  • Try a different browser (Chrome recommended)

Cover Image Errors

"Image too small"

Minimum size: 600×900 pixels

  • Resize your cover image to at least 1600×2400 pixels for best quality

"Image format not supported"

Supported formats: JPG, PNG, WebP

  • Convert from other formats using any image editor

"Image too large"

Maximum size: 10 MB

  • Reduce resolution or use JPG (which compresses better than PNG)

Metadata Errors

"Title is required"

Every book needs a title. Fill in the Title field.

"ISBN format invalid"

If entering an ISBN:

  • ISBN-10: 10 digits (including check digit)
  • ISBN-13: 13 digits starting with 978 or 979
  • Remove any hyphens or spaces before entering

Still Having Issues?

  1. Try in an incognito/private browser window
  2. Clear your browser cache
  3. Try a different browser
  4. Contact support with the error message and a description of what you tried

Related Articles

  • Uploading Your First Book
  • Uploading ePub & PDF Manuscripts
  • Book Cover Images — Requirements & Best Practices

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