An open standard digital book format designed for easy reading across devices
EPUB (Electronic Publication) is an open standard file format for digital books and publications. Developed by the International Digital Publishing Forum (IDPF), it has become the industry standard for digital publishing, now maintained by the World Wide Web Consortium (W3C).
EPUB was designed to provide a single digital publication format that publishers and conversion houses could use in-house, as well as for distribution and sale to consumers. The format allows for reflowable content that adapts to different screen sizes, making it ideal for mobile reading.
At its core, EPUB is essentially a ZIP archive containing HTML, CSS, images, and metadata files structured in a specific way. This web-based approach makes it highly adaptable and accessible across a wide range of devices and platforms.
EPUB files use a container format based on ZIP, with specific organizational requirements. The format contains mandatory metadata, a manifest of included files, and a defined reading order. Recent EPUB versions support advanced features like interactivity, media overlays, and accessibility features.
The primary use case for EPUB is distributing commercial and non-commercial e-books. The format's reflowable nature makes it ideal for text-heavy content that readers consume on a variety of devices, from smartphones to dedicated e-readers.
EPUB 3's enhanced capabilities make it suitable for digital magazines and other publications that combine text with rich media. The format allows for integrating interactive elements while maintaining accessibility.
Many organizations distribute technical documentation, manuals, and guides in EPUB format because of its searchability, hyperlinking capabilities, and cross-platform compatibility.
Educational institutions and academic publishers use EPUB for textbooks and scholarly works. The format's support for notes, citations, and complex layouts makes it suitable for academic content.
EPUB's built-in accessibility features make it a go-to format for creating publications accessible to people with visual impairments or reading disabilities, supporting text-to-speech, alternative text for images, and navigational aids.
EPUB files can be read on a wide range of devices:
Numerous applications support EPUB reading:
There are three major versions of EPUB with different levels of support:
| Feature | EPUB | MOBI | AZW | HTML | |
|---|---|---|---|---|---|
| Reflowable Text | |||||
| Layout Preservation | |||||
| Device Compatibility | |||||
| Interactive Features | |||||
| Accessibility | |||||
| Open Standard |
EPUB excels at providing a flexible reading experience with reflowable text, while PDF is better for preserving exact layouts. MOBI and AZW (Amazon's formats) are more limited in features but have their own ecosystem advantages. HTML provides maximum flexibility but lacks the packaging and standardization of dedicated e-book formats.
Save your document with proper heading styles, as these will translate to EPUB navigation. Include a table of contents before conversion. Remove any complex formatting or tables that aren't essential to the content.
PDF to EPUB conversion can be challenging because PDFs store fixed layouts. Text-based PDFs convert better than scanned documents. Expect to do some cleanup after conversion, particularly with formatting and images.
HTML is structurally similar to EPUB content, making conversion relatively straightforward. Use semantic HTML tags, and ensure your CSS is compatible with e-reader limitations. Remove scripts and external dependencies.
Converting EPUB to PDF creates a fixed layout from reflowable content. Consider page size, margins, and font size for the target device. Test the resulting PDF on multiple screen sizes.
Use Calibre or Amazon's Kindle Previewer for best results. Be aware that some EPUB 3 features may not be supported. Test the converted file on target devices or emulators.
Converting to plain text will lose all formatting, images, and hyperlinks. This should be done only when the text content alone is needed.