Package Structure · E-MIME

Incorrect or missing mimetype / manifest entries

Your EPUB's mimetype file or manifest doesn't correctly declare all the files inside the package, which is a hard requirement for EPUB validity.

Error: Incorrect or missing mimetype / manifest entries
Category: Package Structure
Severity: error
Auto Repair: Supported
Rule ID: E-MIME
Affected: KDP=reject, Apple=reject, Google=reject, Kobo=reject

Why this happens

• mimetype file missing, wrong content, or compressed / not stored first in the zip.
• Files present in the zip but absent from the OPF manifest.
• Manifest hrefs pointing at paths that are not in the package.
• Wrong media-type for an item (e.g. XHTML declared as plain text).

How platforms treat it

How Cermify detects it

1. Confirm zip root contains an uncompressed mimetype entry with exact payload application/epub+zip.
2. Enumerate package files and compare to OPF manifest hrefs.
3. Flag undeclared files and missing href targets.
4. Spot-check media-type values for common resource kinds.

Automatic repair

Cermify can rewrite a correct mimetype entry and add/remove manifest rows for undeclared or missing resources when paths are unambiguous. Media-type guesses follow standard EPUB mappings.

Manual fix

1. Ensure the first zip entry is stored (not deflated) mimetype = application/epub+zip.
2. Add a manifest <item> for every resource used by the book (text, CSS, images, fonts, NCX/nav).
3. Delete manifest rows for files you removed; delete orphan files or declare them.
4. Validate with epubcheck before KDP upload.

Examples

Correct mimetype bytes and a complete manifest are required.

Incorrect

mimetype → application/zip
<!-- chapter2.xhtml on disk but not in manifest -->

Correct

mimetype → application/epub+zip
<item id="c2" href="chapter2.xhtml" media-type="application/xhtml+xml"/>

FAQ

Why does unzipping and rezipping break mimetype?

Many zip tools compress all files and reorder entries. EPUB requires mimetype uncompressed and first. Use an EPUB-aware packager.

Are META-INF files listed in the manifest?

container.xml lives under META-INF and is not a manifest item. Content files referenced by the OPF must be declared.

Can extra undeclared files pass KDP?

Often no—epubcheck reports undeclared resources. Keep the package lean and fully declared.

Related errors

• Missing required metadata (title, language, identifier)
• Reading order (spine) is empty or broken
• Font file not declared in manifest
• Referenced image file is missing

References

• EPUB OCF — mimetype
• EPUB manifest
• Cermify Rule Set kdp-epub-2026-07