# EPUBCheck PKG-026: non-font file obfuscated, how to fix it

Source: https://epubcc.com/epubcheck/pkg-026/ (updated 2026-11-04)

EPUBCheck PKG-026 is an error message: “Obfuscated resource must be a Font Core Media Type (was declared as "…" in "…").” A file that is not a font is listed as obfuscated in META-INF/encryption.xml. Font obfuscation, the scrambling EPUB defines to discourage copying embedded fonts, only applies to font files.

- Official message (EPUBCheck 5.4.0): Obfuscated resource must be a Font Core Media Type (was declared as "%1$s" in "%2$s").
- Default severity: Error

## Typical causes

- An encryption.xml copied from another book that lists files this book does not use as fonts.
- A tool that obfuscated every resource instead of only the fonts.

## How to fix it

1. Find the entry named in the message in META-INF/encryption.xml.
2. Remove the entry for the non-font file and store that file unobfuscated (restore it from the source).
3. Rebuild and validate again.

## When it's not this

If the file is encrypted with DRM rather than obfuscated, EPUBCheck reports the informative RSC-004.

## Sources

- EPUB 3.3, §4.4 Font obfuscation: https://www.w3.org/TR/epub-33/#sec-font-obfuscation (read 2026-11-04)

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