# PKG-012: non-ASCII letters in file name, how to fix it

Source: https://epubcc.com/epubcheck/pkg-012/ (updated 2026-11-04)

EPUBCheck PKG-012 is a usage message: “The file name "…" contains non-ASCII characters, which might create interoperability issues with older reading systems.” A file name inside the EPUB contains non-ASCII characters (accents, other scripts). That is valid in EPUB 3, but it may break older reading systems, so EPUBCheck reports it as usage information.

- Official message (EPUBCheck 5.4.0): The file name "%1$s" contains non-ASCII characters, which might create interoperability issues with older reading systems.
- Default severity: Usage

## Typical causes

- Files named after titles in languages other than English, such as "capítulo-1.xhtml".
- Images exported with the caption or the photographer's name as the file name.

## How to fix it

1. Decide whether you target older devices; if not, you can leave the names as they are.
2. If you do, rename the file with ASCII characters only.
3. 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.

## When it's not this

If EPUBCheck cannot extract the archive at all because of the names, that is PKG-027.

## Sources

- EPUB 3.3, §4.2.3 File paths and file names: https://www.w3.org/TR/epub-33/#sec-container-filenames (read 2026-11-04)

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