EPUB submission checklist

Most EPUB rejections come from a handful of structural issues, not content problems. Working through this list before you submit catches the ones that are checkable without a human reviewer.

Packaging

The mimetype file has to exist at the root of the archive, contain exactly application/epub+zip, and — for strict validators — be the first file in the ZIP, stored uncompressed. Some export tools get this subtly wrong, which is invisible until a validator or platform flags it. This is the one issue this site's checker can actually fix for you in the downloaded "corrected" file; everything else on this list needs to be fixed in the tool that generated your EPUB.

Required metadata

The package file needs, at minimum, a dc:title, dc:language, and dc:identifier (typically an ISBN or a UUID). Missing any of these is a common, easy-to-miss failure — especially dc:identifier, which some writing tools don't populate by default.

Manifest and spine integrity

Every file referenced in the manifest has to actually exist in the archive, and every item in the reading order (the spine) has to reference a manifest entry that exists. Broken references here usually come from renaming or deleting a file after the EPUB's internal structure was already generated.

Cover image

A cover has to be explicitly declared, not just present as a file — see why EPUB covers get rejected for the specific ways this breaks.

EPUB3 navigation document

EPUB3 files are expected to include a navigation document — a manifest item marked with properties="nav" — separate from any legacy NCX table of contents. Its absence is flagged as a warning rather than an outright failure, but it's expected by most modern reading systems.

Image size

Images over roughly 5MB are a frequent, avoidable cause of slow processing or a size-based rejection — most often from reusing print-resolution art without resizing it for screen reading.

What this checklist doesn't cover

This is a structural checklist, not a substitute for the official EPUBCheck validator or a platform's own review — content issues, accessibility requirements, and platform-specific policies aren't covered here or by this site's checker.

Run through this list automatically: upload your file to the EPUB format checker.