# EPUBCheck HTM-044: unused namespace declared, how to fix it

Source: https://epubcc.com/epubcheck/htm-044/ (updated 2026-11-04)

EPUBCheck HTM-044 is a usage message: “Namespace uri "…" was included but not used.” A namespace is declared in a document but never used. It is a usage note: harmless, reported only so you can tidy the markup, and it does not make the EPUB invalid.

- Official message (EPUBCheck 5.4.0): Namespace uri "%1$s" was included but not used.
- Default severity: Usage
- EPUBCheck's suggestion: Remove unused Namespace URIs.

## Typical causes

- Declarations copied from a template, such as xmlns:svg or xmlns:m on every chapter.
- Markup that used the namespace once and was later removed by an editor.

## How to fix it

1. Open the file EPUBCheck names (the message gives the path, line and column) in a text or EPUB editor such as Sigil, or unzip the EPUB and open it there.
2. Remove the unused xmlns declaration that EPUBCheck names from the html element.
3. Keep declarations that other chapters use, such as xmlns:epub, only where they are needed.
4. Rebuild the EPUB and run EPUBCheck again to confirm the message is gone.

## When it's not this

If the epub prefix points to the wrong URI, that is HTM-010, not HTM-044.

## Sources

- EPUBCheck 5.4.0 message texts (MessageBundle.properties, w3c/epubcheck on GitHub): https://github.com/w3c/epubcheck/blob/v5.4.0/src/main/resources/com/adobe/epubcheck/messages/MessageBundle.properties (read 2026-11-04)

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