# EPUBCheck CSS-028: font-face declaration used, how to fix it

Source: https://epubcc.com/epubcheck/css-028/ (updated 2026-11-04)

EPUBCheck CSS-028 is a usage message: “Use of Font-face declaration.” The book declares fonts with @font-face. This is a usage note shown only with EPUBCheck's -u option, to record that the book embeds or references fonts; it is not a problem in itself.

- Official message (EPUBCheck 5.4.0): Use of Font-face declaration.
- Default severity: Usage

## Typical causes

- Any stylesheet that embeds a font with @font-face.
- Fonts added by a conversion or design tool for headings, drop caps or non-Latin scripts.

## How to fix it

1. Nothing to fix because of this note.
2. Check that each font's licence allows embedding, and that each font file is in the manifest with a core font media type (font/woff2, font/woff, font/otf or font/ttf).
3. Remember that many reading apps let readers override embedded fonts, so the text must work without them.

## When it's not this

If the font format is not a core type, EPUBCheck adds CSS-007; an empty rule is CSS-019.

## Sources

- EPUB 3.3, §3.2 Core media types: https://www.w3.org/TR/epub-33/#sec-core-media-types (read 2026-11-04)
- EPUBCheck wiki: Running EPUBCheck (command-line options): https://github.com/w3c/epubcheck/wiki/Running (read 2026-11-04)

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