Why Does Amazon KDP Reject Ebooks?

1. EPUB validation failures

KDP runs a version of EPUBCheck on uploaded files. Critical errors — missing spine items, broken manifest references, corrupted font files — will block the upload entirely. KDP's error messages are often less descriptive than EPUBCheck's own output, so running your file through EPUBCheck directly before uploading gives you the cleaner diagnosis.

2. Oversized or unsupported images

KDP enforces a total file size limit. Images larger than their display size waste space and push files over the limit. KDP requires images to be JPG or GIF inside the EPUB — PNG images work on most platforms but can occasionally trigger processing errors in KDP's conversion pipeline.

3. Missing or incomplete metadata

The dc:title and dc:creator fields in content.opf must be present and non-empty. A book title that exactly matches an existing title on Amazon can trigger a duplicate content review. The language attribute must be a valid BCP 47 language code (e.g., "en", "en-US").

4. NCX or TOC structure errors

KDP's conversion pipeline reads the NCX to build the Kindle's chapter navigation. A missing NCX, broken navPoint references, or an NCX listing chapters not in the spine causes the Kindle version to have a broken or empty table of contents — KDP may reject this or produce a file that fails Quality Review.

5. Content policy flags

KDP scans uploaded content against its content guidelines. Books with prohibited content categories, titles or descriptions that trigger keyword filters, or covers that violate content policies are flagged for human review. AI-generated content declarations are now required in some categories.

6. Duplicate content

Uploading a book with the same or very similar content to an existing ASIN — including your own — can trigger a quality flag. This is common when authors upload a second edition without clearly differentiating the title and content, or when a free preview is uploaded separately as a full book.

Does KDP accept EPUB 3 files?

Yes, KDP accepts EPUB 3, EPUB 2, and DOCX. EPUB 3 is the preferred format. KDP converts all uploaded files to Kindle Format (KFX/MOBI8) before delivery, so the EPUB you upload is the source, not the delivered format.

How long does KDP take to review a flagged book?

Automated upload rejections are immediate. Content policy reviews typically take 1–5 business days. If your book has been in review for more than 7 days, KDP support can provide a status update.

Can I upload a DOCX instead of EPUB to avoid validation errors?

Yes, but the trade-off is less control over the final output. KDP's DOCX-to-Kindle conversion handles basic formatting well but can produce inconsistent results with complex layouts, custom fonts, or tables. A validated EPUB gives you more predictable output.