EPUB Error: NCX navPoint Mismatch (TOC Links to Wrong or Missing Chapters)
What causes this error?
An NCX navPoint mismatch means your ebook's table of contents links to the wrong chapters or to anchor IDs that no longer exist in the target file. It happens when chapters are reordered after the NCX was generated, when anchor IDs in the NCX reference headings that were renamed or removed, or when the conversion tool builds the NCX from an intermediate file list that doesn't match the final chapter filenames.
How to fix it
- Open toc.ncx and list all
<content src="..."/>values — write out the chapter files and anchor IDs each navPoint references. - For references that include a fragment (e.g.,
#ch3-start), open the target chapter file and confirm the id exists — search forid="ch3-start". If missing, either add the anchor to the chapter or update the navPoint src to remove the fragment. - Compare the navPoint order in toc.ncx against the
<itemref>order in the OPF<spine>— they should match. If chapters were reordered, update the navPoint sequence to match the spine. - The fastest complete fix: regenerate the NCX from your current chapter structure using Calibre (Edit Book → Tools → Table of Contents → Generate TOC from document) or Sigil (Tools → Table of Contents → Generate Table of Contents).
- After regenerating, open in Kindle Previewer and test every TOC entry: click each chapter link and verify it lands on the correct chapter heading.
Common questions
How is a navPoint mismatch different from a broken spine?
The spine controls sequential reading order — what "next page" means when paging through continuously. The NCX controls the navigational TOC users see when tapping "Go To" or opening the chapter list. They can diverge independently: a spine in the wrong order shows chapters out of sequence when reading through; an NCX mismatch sends users to the wrong chapter when tapping a title, but the sequential read still works. Both need to be correct.
EPUBCheck didn't flag a chapter order problem — why is Kindle still navigating to the wrong chapter?
EPUBCheck can detect missing anchor references (NCX-002) but doesn't validate whether the navPoint sequence matches your intended reading order, since it has no way to know what that order should be. Order mismatches are a logical error, not a structural one — EPUBCheck sees a valid NCX, just one whose chapter sequence differs from the spine.
Check your EPUB before uploading
The free EPUB Validator catches structure, metadata, and navigation errors — no signup, no Java, runs in the browser.
Validate Your EPUB Free →Building your EPUB correctly from the start prevents most of these errors before they happen. See the EPUB formatting guide for the full workflow: manuscript cleanup, TOC, front matter, EPUB 3.0 generation, and validation.
Common EPUB errors: Missing NCX navigation table
Platform rejection guides: Why Amazon KDP rejects ebooks