EPUB Error: Missing EPUB 3 Navigation Document (nav.xhtml)

RSC-019: an EPUB 3 Publication must include a Navigation Document. Or: manifest item with "nav" property not found in the package

What causes this error?

EPUB 3 requires a Navigation Document — an XHTML file that provides machine-readable structure for the book's table of contents, landmarks, and page list. This file must be declared in the OPF manifest with properties="nav". Without it, EPUBCheck issues RSC-019 and the publication fails EPUB 3 validation. The navigation document is distinct from and cannot be substituted by the EPUB 2 NCX file (toc.ncx): the NCX is optional in EPUB 3, kept only for backwards compatibility with older reading systems, but nav.xhtml is mandatory. The most common cause is export from tools that generate EPUB 2-style packages while declaring version="3.0" in the OPF — they produce a toc.ncx without adding a nav.xhtml, which satisfies EPUB 2 requirements but fails EPUB 3 validation on every strict platform.

How to fix it

  1. Open content.opf and check the <package> element's version attribute — if it says version="3.0", your EPUB is an EPUB 3 publication and requires a navigation document.
  2. Search the manifest for an item with properties="nav" — this identifies the navigation document. If absent, either the nav file is missing from the package or it exists but lacks the required properties attribute.
  3. In Calibre: open your EPUB in Edit Book, go to Tools → Table of Contents → Insert Inline Table of Contents. Calibre creates an EPUB 3-compatible navigation document and registers it in the manifest automatically.
  4. In Sigil: open the EPUB and go to Tools → Generate Table of Contents — Sigil handles nav.xhtml creation for EPUB 3 packages and adds the correct manifest entry.
  5. Re-validate with EPUBCheck after adding or restoring the navigation document, and confirm RSC-019 is cleared. Open the EPUB in Kindle Previewer or Apple Books to verify chapter navigation works from the TOC.

Common questions

My EPUB has a toc.ncx — why does it still fail with RSC-019?

toc.ncx is the EPUB 2 navigation file and is optional in EPUB 3. RSC-019 is specifically about the EPUB 3 Navigation Document (nav.xhtml), which is a different file that serves the same purpose under the newer specification. An EPUB 3 publication must have nav.xhtml even if it also includes a toc.ncx for backwards compatibility — one does not substitute for the other.

Should EPUB 3 files include both nav.xhtml and toc.ncx?

nav.xhtml is required for EPUB 3. toc.ncx is optional but recommended for wide compatibility — older Kindle devices, some Kobo firmware versions, and certain library distribution systems still expect an NCX for chapter navigation. Including both nav.xhtml and toc.ncx is the safest approach for broad distribution.

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 (EPUB 2), NCX navPoint mismatch

Platform rejection guides: Why Apple Books rejects ebooks, Why OverDrive rejects ebooks (library distribution)