How to create a package file like package.opf for an EPUB 3.1 book?

At least one package file, like package.opf, is required for an EPUB 3.1 book in the book ZIP container. It defines required meta data and specifies 2 required content files.

Here is the requirement on a package file:

1. A package file must be named with .opf file extension.

2. A package file must be an XML file and meet the EPUB Packages 3.1 specifications.

3. A package file must specify version="3.1" in the "package" XML element.

4. A package file must specify a unique-identifier and several meta data elements. For example:

    <dc:title>Hello</dc:title>
    <dc:identifier id="id">fyicenter.com.epub.hello</dc:identifier>
    <dc:language>en-US</dc:language>
    <meta property="dcterms:modified">2018-04-01T00:00:00Z</meta>

5. A package file must specify at least 2 XHTML files: one provides navigation information of the book, and the other provides the content of the book.

6. A package file can be placed in any directory of the EPUB 3.1 book ZIP container. But its exact location must be specified correctly in the "container.xml" file.

You can create a package file with any text editor. Here is an example called package.opf:

<?xml version="1.0" encoding="UTF-8"?>
<!-- package.opf
  Copyright (c) FYIcenter.com 
-->
<package xmlns="http://www.idpf.org/2007/opf" version="3.1" 
  unique-identifier="id">
  <metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
    <dc:title>Hello</dc:title>
    <dc:identifier id="id">fyicenter.com.epub.hello</dc:identifier>
    <dc:language>en-US</dc:language>
    <meta property="dcterms:modified">2018-04-01T00:00:00Z</meta>
  </metadata>
  <manifest>
    <item id="navigation" href="navigation.xhtml" 
      media-type="application/xhtml+xml" properties="nav"/>
    <item id="content" href="content.xhtml" media-type="application/xhtml+xml"/>
  </manifest>
  <spine>
    <itemref idref="content"/>
  </spine>
</package>

Download Hello-3.1.epub, and unzip it. You see an example of "package.opf" in the root directory.

⇒ Hello-3.1.epub - Navigation File: navigation.xhtml

⇐ Hello-3.1.epub - "container.xml" File

⇑ Introduction of EPUB 3.1 Specification

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