# EPUBCheck PKG-023: validating as EPUB 2.0, how to fix it

Source: https://epubcc.com/epubcheck/pkg-023/ (updated 2026-11-04)

EPUBCheck PKG-023 is a usage message: “Validating the EPUB against version 2.0, default validation profile will be used.” EPUBCheck is validating the file as EPUB 2.0 and applying its default validation profile. It is a usage message, shown only with -u, and it does not mean anything is wrong.

- Official message (EPUBCheck 5.4.0): Validating the EPUB against version 2.0, default validation profile will be used.
- Default severity: Usage

## Typical causes

- The package document declares version="2.0", so EPUBCheck checks it against the EPUB 2 rules.
- EPUBCheck was run with -v 2.0 on purpose.

## How to fix it

1. Nothing to fix if the book is meant to be EPUB 2.
2. If you meant to produce EPUB 3, update the package to version="3.0" with the required EPUB 3 metadata and a navigation document, then validate again.
3. New books should be EPUB 3: current reading apps and Send to Kindle read it.

## When it's not this

If the version you asked for differs from the one the file declares, the warning is PKG-001.

## Sources

- EPUB 3.3, §5.9 Legacy features: https://www.w3.org/TR/epub-33/#sec-pkg-legacy (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.