# EPUBCheck HTM-003: External entities are not allowed in…

Source: https://epublab.com/epubcheck/htm-003/ (updated 2026-11-03)

EPUBCheck HTM-003 is an error message: “External entities are not allowed in EPUB v3 documents. External entity declaration found: ….” An EPUB 3 document declares an external entity, which is not allowed.

- Official message (EPUBCheck 5.4.0): External entities are not allowed in EPUB v3 documents. External entity declaration found: %1$s.
- Default severity: Error

## Typical causes

- A DOCTYPE with an internal subset that declares entities from an external file.

## How to fix it

- Remove the entity declarations and write the characters directly or as numeric references.

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