Digital publishing
Ebook & Audiobook Formats Explained
Which file to make for which store — and which formats are obsolete.
Formats at a glance
| Format | Extension | Layout | DRM | Where it is used |
|---|---|---|---|---|
| EPUB 3 | .epub | Reflowable or fixed | Optional | Apple Books, Kobo, Google Play, Barnes & Noble, libraries; accepted by KDP for conversion |
| EPUB 2 | .epub | Reflowable | Optional | Legacy readers; most stores now prefer EPUB 3 |
| KPF (Kindle Package Format) | .kpf | Reflowable or fixed | Amazon | Amazon Kindle (KDP) |
| KF8 / AZW3 | .azw3 | Reflowable or fixed | Amazon | Kindle devices and apps (delivery format) |
| MOBI (legacy) | .mobi | Reflowable | Optional | Deprecated for KDP uploads of reflowable books |
| Fixed-Layout EPUB | .epub | Fixed | Optional | Apple Books, Kobo, Google Play; Kindle via Kindle Create or Kids' Book Creator |
| Fixed | Optional | Direct sales, Google Play; the standard file for print-on-demand interiors | ||
| Kindle Print Replica | (from PDF) | Fixed | Amazon | Amazon Kindle (textbooks and complex layouts) |
| CBZ / CBR (Comic Book Archive) | .cbz / .cbr | Fixed | None | Comic reader apps, direct sales |
| DOCX (upload format) | .docx | Converted to reflowable | — | Accepted for conversion by KDP, Draft2Digital and others |
| Audiobook (MP3 masters) | .mp3 | Audio | Retailer | Audible / ACX, Findaway Voices (Spotify), Apple, Google Play, Kobo |
Ebook cover images
Retailers display covers as small thumbnails, so design at full size and test small. KDP recommends 2,560 x 1,600 px (a 1.6:1 height-to-width ratio); many other stores accept a 2:3 ratio such as 1,600 x 2,400 px. Use RGB JPEG at high quality.