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PKG-005: mimetype has a ZIP extra field

Plain English meaning

The EPUB has a mimetype file, but the ZIP entry contains extra metadata. EPUBCheck rejects this because the mimetype entry must be very plain: first in the package, uncompressed, and without ZIP extra fields.

Why it happens

• The EPUB was repacked by a ZIP program that added extra metadata.
• A repair tool or file manager changed the ZIP entry attributes.
• The EPUB was copied through a workflow that rewrote the ZIP container.

What you can check yourself

This one is harder to inspect visually. The file may look fine when opened as a ZIP, but EPUBCheck still sees the ZIP extra field. The practical check is to repack the EPUB with the proper EPUB ZIP rules and rerun EPUBCheck.

What can usually be fixed

If the book content is otherwise valid, this is usually a small container-level fix. Rebuild the EPUB ZIP package so that mimetype is stored first, uncompressed, with no extra field.

What cannot be promised

Fixing PKG-005 only fixes the packaging rule. It does not fix missing images, broken links, layout issues, metadata problems, or retailer-specific publishing rules.