# What is font obfuscation?

Source: https://epubcc.com/glossary/font-obfuscation/ (updated 2026-11-04)

Font obfuscation is a simple scrambling of embedded font files, keyed to the EPUB's unique identifier and declared in META-INF/encryption.xml, so a font cannot be copied out of the ZIP and installed elsewhere. EPUB 3.3 says it is not encryption and offers no real protection.

## Why it matters when you convert a PDF to EPUB

It exists because some font licences allow embedding only if the font is tied to the book. It matters when you edit or rebuild an EPUB: changing the unique identifier breaks obfuscated fonts, and obfuscating anything that is not a font is an error.

EPUBCheck reports a non-font file listed as obfuscated with PKG-026, and its usage message OBS-001 can name font obfuscation as an outdated feature.

How EpubCC handles it: the engine embeds no fonts, so there is nothing to obfuscate and its EPUBs have no encryption.xml. The reader's own fonts are used instead.