# EPUBCheck PKG-007: The content of the mimetype file must…

Source: https://epublab.com/epubcheck/pkg-007/ (updated 2026-11-03)

EPUBCheck PKG-007 is an error message: “The content of the mimetype file must be the string "application/epub+zip"….” The mimetype file must contain exactly the text application/epub+zip, with nothing before or after it.

- Official message (EPUBCheck 5.4.0): The content of the mimetype file must be the string "application/epub+zip"%1$s
- Default severity: Error

## Typical causes

- A trailing newline or space added by a text editor.
- A different value, such as a typo or another media type.

## How to fix it

- Recreate the file without a newline, for example with printf 'application/epub+zip' > mimetype, then rebuild the archive with mimetype first: 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.