What Is EPUB? Complete Guide to the eBook Format
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
Common Mistakes to Avoid
Assuming EPUB works on Kindle. Amazon Kindle devices do not natively support EPUB. You need to convert EPUB to MOBI or KPF using Calibre or Amazon's Send to Kindle tool. Amazon has been improving EPUB support, but for reliable Kindle compatibility, always convert first.
Creating an EPUB from a complex PDF. PDF-to-EPUB conversion works best for text-heavy documents. PDFs with complex layouts, multiple columns, infographics, and precise positioning will not convert cleanly to EPUB's reflowable format. For these documents, sharing the PDF directly via Linkyhost provides a better reading experience.
Not testing on multiple readers. EPUB rendering varies across reading apps. A book that looks perfect in Apple Books may have spacing issues in Google Play Books or a different e-reader. Test your EPUB on at least two different readers before distributing.
Publishing without a proper cover image. Most e-reader apps display the cover image in the library view. An EPUB without a cover appears as a blank thumbnail, which looks unprofessional and reduces the chance someone will open it.
Ignoring metadata. Title, author, language, and description metadata are used by e-readers to organize and display your book. Fill in all metadata fields during creation to ensure your EPUB appears correctly in readers' libraries.
EPUB Creation Tools Compared
| Tool | Free | Platform | Best For |
|---|---|---|---|
| Sigil | Yes | Windows, Mac, Linux | Manual EPUB editing |
| Calibre | Yes | Windows, Mac, Linux | Converting and managing ebooks |
| Pages | Yes (Mac) | macOS | Quick EPUB export from documents |
| Pandoc | Yes | Command line | Batch conversion from Markdown/DOCX |
| Vellum | Paid ($249) | macOS | Professional book formatting |
| Atticus | Paid ($147) | Browser | Professional formatting, cross-platform |
EPUB vs Other eBook Formats
| Format | Open Standard | Reflowable | DRM Support | Primary Platform |
|---|---|---|---|---|
| EPUB | Yes | Yes | Optional | Most e-readers |
| MOBI | No (Amazon) | Yes | Amazon DRM | Kindle (legacy) |
| KFX/KPF | No (Amazon) | Yes | Amazon DRM | Kindle (current) |
| Yes | No | Optional | Universal | |
| AZW3 | No (Amazon) | Yes | Amazon DRM | Kindle |
Frequently Asked Questions
Can I share an EPUB file with a link?
Yes. Upload your EPUB file to Linkyhost and get a shareable link. Recipients can download the file and open it in their preferred reading app. For recipients who do not have an EPUB reader, consider converting to PDF first and sharing that version via Linkyhost for in-browser reading.
How do I convert a Word document to EPUB?
Use Calibre (free, desktop) or Pandoc (free, command line). In Calibre, click "Add books" to import your DOCX, then click "Convert books" and select EPUB as the output format. The conversion preserves text, headings, and basic formatting. Complex layouts may need manual adjustment in Sigil after conversion.
Is EPUB or PDF better for sharing documents?
It depends on the content. EPUB is better for long-form reading material (books, novels, manuals) because readers can adjust font size and the text reflows to fit any screen. PDF is better for documents where layout matters (forms, brochures, reports, presentations) because the layout is fixed and displays identically on every device. For professional document sharing, host PDFs on Linkyhost for the most reliable cross-device experience.