ERROR(OPF-030) - unique-identifier Not Found


How to fix the "ERROR(OPF-030) - The unique-identifier ... was not found" error?



When you validate a EPUB 2.0 package with EpubCheck, you may see the following error:

C:\fyicenter> java -jar epubcheck.jar Error-Unique-ID-Not-Found-2.0.epub
Validating using EPUB version 2.0.1 rules.
ERROR(OPF-030): Error-Unique-ID-Not-Found-2.0.epub/package.opf(-1,-1): 
  The unique-identifier "MyID" was not found.

Check finished with errors
Messages: 0 fatals / 1 error / 0 warnings / 0 infos

EPUBCheck completed

Download Error-Unique-ID-Not-Found-2.0.epub, and unzip it. You see the "package.opf" file in the root directory.

<?xml version="1.0" encoding="UTF-8"?>
<!-- package.opf
  Copyright (c) 2018 
<package xmlns="" version="2.0" 
  <metadata xmlns:dc="">
    <dc:identifier id="id"></dc:identifier>

    <item id="navigation" href="/navigation.xml" 
    <item id="content" href="/content.xhtml" 
  <spine toc="navigation">
    <itemref idref="content"/>

The error is caused by the mis-matching values given in the (<package ... unique-identifier="MyID">) element and the (<dc:identifier id="id">) element. You can fix the error by changing id="id" to id="MyID".


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2022-11-04, 682🔥, 0💬