What Is EPUB? Complete Guide to the eBook Format
3 min read
Learn what EPUB files are, how they work, and how to open, create, and convert them. A complete guide to the most popular eBook format.
EPUB (Electronic Publication) is the most widely used open eBook format. It is supported by virtually every e-reader, tablet, and reading app except Amazon Kindle (which uses its own formats but can convert EPUB).
How EPUB Works
An EPUB file is essentially a ZIP archive containing:
- XHTML files — The actual book content (text and formatting)
- CSS stylesheets — Visual styling (fonts, colors, layout)
- Images — Embedded illustrations, photos, and cover art
- Metadata — Title, author, language, publisher info
- Navigation — Table of contents and reading order
The key feature of EPUB is reflowable text — content adapts to the screen size and reader preferences. Readers can adjust font size, font family, and margins, and the text reflows naturally.
EPUB vs PDF
| Feature | EPUB | |
|---|---|---|
| Text reflow | Yes | No (fixed layout) |
| Adjustable fonts | Yes | No |
| Best for | Books, long-form reading | Forms, print layouts |
| File size | Usually smaller | Usually larger |
| Reader support | E-readers, apps | Universal |
How to Open EPUB Files
Desktop
- Calibre — Free, open-source e-book manager (Windows, Mac, Linux)
- Apple Books — Built into macOS
- Adobe Digital Editions — Free reader from Adobe
Mobile
- Apple Books — Built into iOS
- Google Play Books — Upload EPUBs to your library
- Lithium (Android) — Lightweight EPUB reader
- KOReader — Open-source reader for various platforms
Online
- Upload the EPUB file to Linkyhost to view it in a browser without installing any software
How to Create an EPUB
- Sigil — Free, open-source EPUB editor with a visual interface
- Calibre — Convert documents to EPUB from many formats
- Pages (Mac) — Export directly to EPUB from Apple's word processor
- Pandoc — Command-line tool that converts Markdown, Word, and other formats to EPUB
How to Convert EPUB
Common conversions:
- EPUB to PDF — Use Calibre or an online converter
- EPUB to MOBI/KPF — Use Calibre or Amazon's Kindle Previewer for Kindle compatibility
- DOCX to EPUB — Use Calibre or Pandoc
- PDF to EPUB — Possible but results vary depending on the PDF's complexity
Tips
- EPUB 3 supports audio, video, and interactive content
- DRM-protected EPUBs require specific reader apps authorized to your account
- For sharing an EPUB with someone who does not have a reader app, convert it to PDF first or host it with a shareable link on Linkyhost