An EPUB (short for electronic publication) file is a widely used open eBook format that is designed for reflowable content, meaning it can adapt its layout to fit various screen sizes—unlike PDFs, which preserve a fixed layout.
Key Features of EPUB
- Reflowable Text: The content adjusts to screen size, font preferences, and orientation. This is ideal for smartphones, tablets, and e-readers like Kobo or Apple Books.
- HTML + CSS Based: Internally, an EPUB file is a compressed archive (
.zip) that contains HTML files, images, stylesheets, metadata, and a manifest. - Navigation: It supports table of contents, internal links, and chapters for easy navigation.
- Supports Rich Media: EPUB 3 can include audio, video, interactive elements, and MathML.
How EPUB Shows “Pages”
EPUB doesn’t have fixed “pages” like PDF. Instead:
- The reading software (like Apple Books, Calibre, or Kobo) dynamically splits content into pages based on screen size, font size, and user settings.
- Pages can vary in number depending on:
- Device screen resolution
- Font size or style
- Margin settings
Because of this, you can’t refer to a fixed page number universally across devices.
EPUB vs PDF
| Feature | EPUB | |
|---|---|---|
| Layout | Reflowable | Fixed |
| Usability on small screens | Excellent | Poor |
| Internal format | HTML + CSS + XML | PostScript-based (binary) |
| Navigation | Flexible (TOC, links, metadata) | Static (can have TOC, but fixed) |