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Glossary

What is an EPUB cover image?

Updated:

The cover image of an EPUB 3 is the manifest item marked with the "cover-image" property; reading apps show it as the thumbnail in the library. It is usually a JPEG or PNG of the front cover.

Why it matters when you convert a PDF to EPUB

A PDF has no notion of a cover: the first page may be a cover, a title page or a blank page. A converter can render the first page as the cover image, but it should not invent one, and a missing cover is not an error, just a plainer library thumbnail.

How EpubCC handles it: a full-page image on the first page of the PDF is kept at the start of the book as its cover page; full-page images on other pages are treated as scans and reported. The engine does not yet mark that image with the cover-image property, so some library views show a generic thumbnail instead of the cover.

Related terms

EPUBCheck messages about this

  • OPF-012 Item property "…" is not defined for media type "…".
  • OPF-032 Guide references "…" which is not a valid "OPS Content Document".

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FAQ

What is an EPUB cover image?

The cover image of an EPUB 3 is the manifest item marked with the "cover-image" property; reading apps show it as the thumbnail in the library. It is usually a JPEG or PNG of the front cover.