# What is EPUB, and which eBook files does KDP accept?

Source: https://kdpbook.io/glossary/epub · Updated 2026-10-15

**EPUB**: The open eBook format KDP accepts for Kindle books. It can be reflowable (text adapts to the screen) or fixed layout (pages keep their design).

Checked against KDP Help on 2026-09-28.

EPUB is the open eBook format: a zipped package of XHTML, CSS, images and metadata. KDP accepts EPUB for Kindle eBooks when it follows the Kindle Publishing Guidelines, alongside Word (DOCX) and KPF files from Kindle Create. MOBI is no longer accepted: since August 1, 2021 for reflowable eBooks and March 18, 2025 for fixed-layout ones.

Also called: EPUB3, eBook file.

## The numbers

eBook files KDP accepts:

| Format | What it is | KDP notes |
| --- | --- | --- |
| EPUB | open standard, reflowable or fixed layout | accepted; check it in Kindle Previewer 4 before uploading |
| DOC / DOCX | Word document | recommended; complex formatting may convert less well |
| KPF | Kindle Package Format, made with Kindle Create | recommended |
| PDF | print-style document | accepted in a limited set of languages |
| HTML (ZIP, HTM, HTML), RTF, TXT | text and web formats | accepted |
| MOBI | older Kindle format | no longer accepted |

## Reflowable and fixed-layout EPUB

The same format covers both kinds of eBook. A reflowable EPUB lets the text adapt to the screen and the reader's settings: right for novels and most non-fiction. A fixed-layout EPUB declares its pages as pre-paginated, so every page keeps its design: right for picture books and comics.

## File size costs money on the 70% option

On the 70% royalty option, KDP subtracts a delivery cost based on the converted file size: $0.15 per MB on Amazon.com, with sizes rounded up to the kilobyte. Uncompressed images in an EPUB make every sale cost more.

## Example: the same $4.99 price, two file sizes

A 2 MB novel at $4.99 on Amazon.com earns $3.28 at 70% (after a $0.30 delivery cost) or $1.75 at 35%.

A 25 MB picture book at the same price earns only $0.87 at 70%, because delivery costs $3.75, so the 35% option ($1.75) pays more.

## Common mistakes

- Uploading a MOBI file.
- Skipping Kindle Previewer (version 4 since September 2026, which replaced Kindle Previewer 3): layout problems show up after publishing instead of before.
- Embedding full-resolution print images, which inflates the file and the delivery cost.
- Uploading the print PDF as the eBook: the result reads like a scanned book on a phone.
- Putting text inside images in a reflowable book, where readers can't resize it.

In kdpbook.io: kdpbook exports a Kindle EPUB, reflowable or fixed layout, along with a separate Kindle cover.