# EPUBCheck PKG-006: Mimetype file entry is missing or is…

Source: https://epublab.com/epubcheck/pkg-006/ (updated 2026-11-03)

EPUBCheck PKG-006 is an error message: “Mimetype file entry is missing or is not the first file in the archive.” The mimetype file is missing or is not the first entry of the ZIP archive, so reading apps cannot identify the file as an EPUB from its first bytes.

- Official message (EPUBCheck 5.4.0): Mimetype file entry is missing or is not the first file in the archive.
- Default severity: Error

## Typical causes

- The book folder was compressed with a generic tool that adds files in alphabetical or arbitrary order.
- The mimetype file was deleted while editing the EPUB.

## How to fix it

- Make sure a file named mimetype containing exactly application/epub+zip sits at the root of the book.
- Rebuild the archive with the mimetype file first and stored uncompressed, for example from the folder that contains the book: zip -X0 book.epub mimetype and then zip -rX9 book.epub META-INF OEBPS (use your own folder names).

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EPUBLab.