# EPUBCheck CSS-004: CSS documents must be encoded in UTF-8…

Source: https://epublab.com/epubcheck/css-004/ (updated 2026-11-03)

EPUBCheck CSS-004 is an error message: “CSS documents must be encoded in UTF-8, detected …;.” A CSS file uses an encoding other than UTF-8, which EPUB requires.

- Official message (EPUBCheck 5.4.0): CSS documents must be encoded in UTF-8, detected %1$s;
- Default severity: Error

## Typical causes

- A stylesheet saved as ISO-8859-1 or Windows-1252, or with a @charset rule naming one.

## How to fix it

- Convert the file to UTF-8 and change or remove the @charset rule.

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