What is an EPUB file?
EPUB is the ebook format that reflows text to fit whatever screen you are reading on, so you can change the font size instead of pinching and scrolling. Most e-readers and reading apps open one, the Kindle being the notable exception. EPUB is listed here for reference. It is not one this site can convert.
Specification
| Full name | Electronic Publication |
|---|---|
| Extensions | .epub |
| Media type | application/epub+zip |
| Compression | Lossless |
| Transparency | — |
| Animation | — |
| Multiple pages | Supported |
| Colour depth | ZIP package of XHTML, CSS and an OPF manifest |
| Size limits | — |
| Introduced | 2007 |
| Developed by | International Digital Publishing Forum, now W3C |
| Standard | Open |
| Browser support | Not displayed by browsers |
What EPUB is used for
- Ebooks sold or borrowed for e-readers and reading apps
- Self-published titles distributed outside the Kindle store
- Technical manuals that need to reflow on a phone
- Library lending catalogues, which standardise on EPUB
Strengths and limitations
What EPUB does well
- Text reflows and resizes, so it reads well on small screens
- Open standard built on HTML and CSS, with no licence fees
- Opens on every major e-reader and reading app except the Kindle
Where EPUB falls short
- Layout is a suggestion, so designed pages and complex tables break up
- Reader support for EPUB 3 features such as scripting is inconsistent
- Commercial titles are usually locked with DRM that blocks conversion
Questions about EPUB
What is a .epub file?
EPUB is the ebook format that reflows text to fit whatever screen you are reading on, so you can change the font size instead of pinching and scrolling. The extension .epub identifies it, and its media type is application/epub+zip.
How do I open an EPUB file?
Browsers do not display EPUB natively, so you either need software that understands it or you convert it to something more common first. Converting is usually the faster route when you only need to look at the contents once.
Is EPUB lossy or lossless?
Lossless. Nothing is discarded, so repeated saves never degrade the contents.
What is EPUB good for?
Text reflows and resizes, so it reads well on small screens. Open standard built on HTML and CSS, with no licence fees. Opens on every major e-reader and reading app except the Kindle. In practice that makes it a good fit for ebooks sold or borrowed for e-readers and reading apps, and Self-published titles distributed outside the Kindle store.
What are the drawbacks of EPUB?
Layout is a suggestion, so designed pages and complex tables break up. Reader support for EPUB 3 features such as scripting is inconsistent. Commercial titles are usually locked with DRM that blocks conversion.