# EPUBCheck PKG-009: The file name … contains characters…

Source: https://epublab.com/epubcheck/pkg-009/ (updated 2026-11-03)

EPUBCheck PKG-009 is an error message: “The file name "…" contains characters that are not allowed in OCF file names: ….” A file name inside the EPUB contains a character that the EPUB container rules do not allow in file names.

- Official message (EPUBCheck 5.4.0): The file name "%1$s" contains characters that are not allowed in OCF file names: %2$s.
- Default severity: Error

## Typical causes

- Characters such as ", *, :, <, >, ?, \ or |, or control characters, usually copied from the original title of an image or chapter.

## How to fix it

- Rename the file using letters, digits, hyphens and underscores.
- After renaming, update every reference to the file: the manifest in the package document, links and image sources in the XHTML, and url() references in the CSS.

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