EPUB® documents, unlike print books or PDF files, are designed to change. The content flows, or reflows, to fit
the screen and to fit the needs of the reader. The EPUB 3.0 Specification says that "content presentation should
adapt to the user rather than the user having to adapt to a particular representation of content."
But this principle doesn't work for all types of documents. Sometimes content and design are so intertwined
they cannot be separated. Any change in appearance risks changing the meaning, or losing all meaning. Fixedlayout
documents give content creators greater control over presentation, when a reflowable EPUB is not
suitable for the content.
This document, EPUB 3 Fixed-Layout Documents, defines a set of metadata properties to allow declarative
expression of intended rendering behaviors of fixed-layout documents in the context of EPUB 3. It also defines
mechanisms to express the intended rendering dimensions of fixed-layout XHTML and SVG [ContentDocs30]
content, as well as bitmap images.