Cermify · Error Library · KDP

Package Structure · E-ENC

Non-UTF-8 encoded content file

One of your chapter files isn't encoded as UTF-8, which can cause garbled text or validator failures on Kindle.

Severity
error
Automatic repair
Supported
Submission impact
KDP: reject
Rule ID
E-ENC
Error: Non-UTF-8 encoded content file
Category: Package Structure
Severity: error
Auto Repair: Supported
Rule ID: E-ENC
Affected: KDP=reject, Apple=reject, Google=warning, Kobo=warning
Check this automatically with Cermify

Why this happens

How platforms treat it

PlatformResult
KDPreject
Apple Booksreject
Google Playwarning
Kobowarning

How Cermify detects it

  1. Read each content document's declared encoding.
  2. Detect bytes that are invalid in the declared encoding or strongly indicate another code page.
  3. Flag non-UTF-8 chapter/CSS/XML resources used by the package.
  4. Note mismatches between declaration and actual bytes.

Automatic repair

Cermify can transcode many legacy single-byte chapter files to UTF-8 and normalize XML declarations. Always proof special characters (curly quotes, em dashes, accented letters) after conversion.

Manual fix

  1. Open the flagged file in an editor that shows encoding.
  2. Convert to UTF-8 (without BOM preferred for XHTML).
  3. Set encoding="UTF-8" in the XML declaration and remove conflicting meta charset values.
  4. Repackage and confirm characters render correctly on device preview.

Examples

Content documents should be UTF-8 with a matching declaration.

Incorrect

<?xml version="1.0" encoding="ISO-8859-1"?>
<html xmlns="http://www.w3.org/1999/xhtml">…

Correct

<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">…

FAQ

Is a UTF-8 BOM allowed?

Some pipelines accept BOM; others warn. Prefer UTF-8 without BOM for XHTML in EPUBs.

Why do only some chapters fail?

Exporters sometimes mix encodings when chapters were edited in different tools. Fix each flagged file.

Does this affect fonts?

E-ENC is about text resource encoding, not font binaries. See E-FONT for font declaration issues.

Related errors

References