# EPUBCheck OPF-085: invalid UUID identifier, how to fix it

Source: https://epubcc.com/epubcheck/opf-085/ (updated 2026-11-04)

EPUBCheck OPF-085 is a warning message: “"dc:identifier" value "…" is marked as a UUID, but is an invalid UUID.” A dc:identifier says it is a UUID (urn:uuid:) but the value is not a valid UUID. Reading apps and stores may use the identifier to recognise the book, so a malformed one is reported.

- Official message (EPUBCheck 5.4.0): "dc:identifier" value "%1$s" is marked as a UUID, but is an invalid UUID.
- Default severity: Warning

## Typical causes

- A shortened or mistyped value after urn:uuid:.
- An invented value, such as urn:uuid:my-book-1.
- An ISBN or another identifier written after the urn:uuid: prefix.

## How to fix it

1. Read the value EPUBCheck quotes.
2. Replace it with a real UUID in the form 8-4-4-4-12 hexadecimal digits (any UUID generator makes one).
3. If the identifier is not a UUID, drop the urn:uuid: prefix and write it in its own form, such as urn:isbn:…

## When it's not this

If the package's unique-identifier does not match any dc:identifier, that is OPF-030.

## Sources

- EPUB 3.3, §5.5.3.1.1 The dc:identifier element: https://www.w3.org/TR/epub-33/#sec-opf-dcidentifier (read 2026-11-04)

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