What Is EPUB?
EPUB (Electronic Publication) is an open eBook standard maintained by the W3C. It is the most widely supported eBook format across reading devices and apps, with the notable exception of Amazon's Kindle ecosystem which uses its own proprietary formats.
An EPUB file is essentially a ZIP archive containing XHTML content, CSS stylesheets, images, and metadata packaged according to a defined specification. This structure makes EPUB reflowable — the text adapts to the reader's screen size, font preferences, and accessibility settings.
EPUB vs PDF
| Feature | EPUB | |
|---|---|---|
| Text reflow | Yes — adapts to screen | No — fixed layout |
| Font size adjustment | Reader-controlled | Zoom only |
| Best for | Novels, textbooks, articles | Forms, manuals, print-ready docs |
| Accessibility | Excellent (with proper markup) | Variable |
| File size | Typically smaller | Can be large with embedded fonts/images |
| DRM | Optional (Adobe DRM, LCP) | Optional (Adobe DRM) |
| Reading on mobile | Excellent | Poor (requires zooming and scrolling) |
For long-form reading on phones and e-readers, EPUB is almost always the better format. PDF is better for documents where precise visual layout matters — think architectural plans, tax forms, or print-ready manuscripts.
EPUB vs Kindle Formats
Amazon's Kindle devices use proprietary formats: the older MOBI/AZW and the current KFX. Kindle does not natively read EPUB files.
However, in 2022 Amazon started accepting EPUB uploads from publishers via Kindle Direct Publishing, converting them to KFX internally. If you are a reader with a Kindle, you can convert EPUB to Kindle-compatible formats using Calibre (free, open-source) or by emailing the file to your Kindle's Send-to-Kindle address.
How to Read EPUB Files
Dedicated E-Readers
- Kobo: Native EPUB support on all Kobo readers
- Kindle: Does not read EPUB natively — convert first
- PocketBook: Full EPUB support
Desktop Applications
- Calibre — Free, open-source. Reads, converts, and manages eBook libraries. Available on Windows, macOS, and Linux.
- Apple Books — Built into macOS and iOS. Excellent EPUB rendering.
- Adobe Digital Editions — Required for some DRM-protected EPUBs.
- Thorium Reader — Free, open-source. Good accessibility features.
Mobile Apps
- Apple Books (iOS/iPadOS) — Built-in, polished reading experience
- Google Play Books (Android/iOS) — Upload your own EPUBs to read in the app
- Moon+ Reader (Android) — Highly customisable free reader
- Lithium (Android) — Lightweight, well-designed EPUB reader
Web Browser
There is no native browser support for EPUB files. However, browser-based readers like Readium and epub.js allow web applications to render EPUB content.
Creating EPUB Files
If you need to create an EPUB from existing content:
- Sigil — Free, open-source EPUB editor. Write directly in XHTML or use a WYSIWYG view.
- Calibre — Convert from DOCX, HTML, TXT, or other formats to EPUB.
- Pandoc — Command-line tool that converts Markdown, DOCX, LaTeX, and other formats to EPUB.
- Pages (macOS) — Export to EPUB from Apple's word processor.
EPUB Versions
EPUB 2 (2007) introduced the basic reflowable format. Many older eBooks still use this version.
EPUB 3 (2011, updated 2023) added support for HTML5, CSS3, JavaScript interactivity, multimedia embedding, and significantly improved accessibility features including ARIA roles and media overlays for read-aloud functionality.
Most modern readers support EPUB 3. When creating new eBooks, use EPUB 3 unless you have a specific reason to target very old reading devices.
Frequently Asked Questions
Can I read EPUB on Kindle?
Not directly. Convert the EPUB to MOBI or KFX using Calibre, or email the EPUB to your Kindle's Send-to-Kindle address (Amazon converts it server-side for newer Kindle models).
Is EPUB DRM-free?
EPUB as a format does not require DRM. Publishers may optionally apply DRM (typically Adobe DRM or Readium LCP). Many independent publishers and platforms like Smashwords sell DRM-free EPUBs.
Why does my EPUB look different on different devices?
Because EPUB is reflowable. Each reading app interprets the CSS slightly differently and applies the user's font and size preferences. This is a feature, not a bug — it makes the content accessible across different screen sizes.