What Is EPUB and How Is It Different from MOBI?
TL;DR:EPUB is the universal ebook standard used by Apple Books, Kobo, Barnes & Noble, and most other retailers. MOBI was Amazon’s proprietary format but has been replaced by KPF (Kindle Package Format). When you upload to KDP, you can submit EPUB, DOCX, or KPF files — Amazon converts them to their current format automatically.
Understanding ebook file formats helps ensure your book displays correctly across devices and platforms. While there are several formats, most self-published authors only need to understand a few key ones.
EPUB is the industry standard for ebooks. It is used by nearly every retailer and reading app outside of Amazon, including Apple Books, Kobo, Barnes & Noble, Google Play Books, and library systems like OverDrive and Libby. EPUB files are built using HTML and CSS, which allows text to adapt to different screen sizes.
MOBI is an older format that is no longer relevant for publishing. It was originally used by Amazon Kindle devices, but Amazon has moved to newer formats. Today, KDP does not accept MOBI uploads.
Amazon now uses modern formats like KPF. Kindle Package Format (KPF) supports improved typography, layout control, and compatibility across Kindle devices. When publishing on KDP, you can upload EPUB, DOCX, or KPF files.
The practical setup for most authors is simple:
- Create a clean EPUB file for wide distribution
- Upload EPUB, DOCX, or KPF to Amazon KDP
Most modern tools — including Vellum, Atticus, Draft2Digital, and Calibre — export EPUB files directly. Amazon’s Kindle Create tool produces KPF files optimized for Kindle.
There are two main types of ebook layouts:
- Reflowable ebooks: Text adjusts to screen size and reader preferences (standard for novels and nonfiction)
- Fixed-layout ebooks: Layout stays locked in place (used for children’s books, comics, and highly visual content)
Always preview your ebook before publishing. Different platforms and devices may display formatting differently, especially with images, tables, or complex layouts. Use preview tools or test on multiple devices to catch issues early.
Sources: