EPUB OCF container
The EPUB container must expose the package document through the expected container structure, including META-INF/container.xml and the packaged resources it points to.
EPUB error guide
Mimetype file entry missing or not first
How PKG_006 EPUB mimetype errors affect KDP uploads and when rebuilding the ZIP container can fix them.
Error text
PKG_006: Mimetype file entry is missing or is not the first file in the archive.
When you usually see it
The book content is present, but EPUBCheck fails because the ZIP container was built in the wrong order.
Plain English
What it means inside the EPUB.
An EPUB is a ZIP file with strict packaging rules. The mimetype entry must be first and stored without compression.
This usually happens after manually zipping a folder, using a generic archive tool, or re-exporting from a tool that changed package order.
User checklist
What to inspect before another upload.
These checks keep the repair decision tied to the EPUB package instead of guessing from a generic error code.
- Check whether the EPUB ZIP contains a root-level mimetype file.
- Check whether mimetype is the first ZIP entry and is stored without compression.
- Check whether the package still contains META-INF/container.xml and a valid OPF file after rebuilding.
Standards context
Why this error matters to validators.
EPUBCheck
EPUBCheck evaluates EPUB 2 and EPUB 3 publications against official EPUB specifications and reports structure, package, markup, and reference problems.
Repairability
Can EPUB Fixer repair it?
Safe repair condition
This is usually repairable by rebuilding the EPUB ZIP container with the mimetype file first and uncompressed.
When it stops at diagnosis
If the archive is corrupted, encrypted, or missing core package files, container rebuild alone is not enough.
Before / after example
Before: mimetype is missing or compressed after other ZIP entries. After: mimetype is first and contains application/epub+zip.
Next step
Scan the actual file before editing by hand.
The same error code can come from different files and different causes. Uploading the EPUB lets the report show the affected path and whether the fix is deterministic.
Upload EPUB to scan