Images
When sizing images in flowing EPUB books, container <div> elements are no longer required. To size images, use viewport units to maintain adaptability for various screen sizes. See Interior Image Requirements for examples.
Images should be defined using img tags in the HTML. Styles such as dimensions and positioning should be defined in the CSS.
Links
Removed the sentence that indicated links in EPUBs are underlined and blue by default.
Video Posterframe Art
The posterframe is the image that displays inline in the book. It is usually a clip (or frame) from the video. The posterframe should be the same size and aspect ratio as the video.
Chinese Language Books: Clarification
For Chinese language books, you must specify both the language (zh) and the script (Hans or Hant) portions of the language code. The language code for Simplified Chinese is zh-Hans and the code for Traditional Chinese is zh-Hant. The code must be specified in both the book’s OPF file and in the metadata using the <language> tag. See Apple Books Metadata XML File Annotated in the Apple Books Book Package Specification for information on the <language> tag.
iTunes Connect Section Names
Changed the iTunes Connect module names throughout the guide to match the new section names (for example, “Deliver Your Content” has been changed to “Resources and Help.”