"What format should my ebook be?" has a short answer and a longer one. The short one: EPUB for stores, PDF for everything you deliver yourself. The longer one matters because the format decides how you format the book, and a file that's right for one destination is often wrong for the other.
What are the main ebook formats?
| Format | What it is | Layout | Where it's used |
|---|---|---|---|
| EPUB | The open standard ebook format (EPUB 3 is current) | Reflowable, or fixed-layout | Apple Books, Kobo, Google Play Books, KDP, most reading apps |
| A fixed page, the same everywhere | Fixed | Direct sales, lead magnets, courses, print | |
| KPF | Kindle Package Format, from Kindle Create | Reflowable or fixed | KDP only |
| DOCX | A Word document | Converted by the store | KDP and Draft2Digital accept it as an upload |
| MOBI / AZW3 | Older Kindle formats | Reflowable | Retired for KDP uploads |
Reflowable means the text rewraps to fit the screen and the reader can change the font size. Fixed means each page is set once, like paper. That single difference drives every other choice.
Which ebook format does each store take?
| Destination | Upload |
|---|---|
| Amazon KDP (Kindle) | EPUB, KPF or DOCX are recommended; MOBI is no longer accepted |
| Apple Books | EPUB |
| Kobo Writing Life | EPUB, or DOCX converted on upload |
| Draft2Digital | DOCX or EPUB |
| Your own site, Gumroad, Etsy | Usually PDF, often with an EPUB too |
Amazon ended MOBI uploads for reflowable ebooks in 2021 and, from March 18, 2025, for fixed-layout ones too. If a guide tells you to make a MOBI, it's out of date. Amazon also lists PDF as accepted for some languages, but a PDF converted to a Kindle book usually reads badly; send EPUB. What KDP actually wants from your file has the details.
How do you format a reflowable ebook?
Because the reader controls the screen, formatting an EPUB is mostly about structure, not position:
- Use real headings for chapters. The ebook's table of contents is built from them.
- No manual page breaks or blank lines for spacing. There are no pages to break.
- No headers, footers or page numbers. The reading app handles location.
- Images at a sensible size, with alt text, and no text locked inside them.
- Embed your fonts if you care about them, knowing many readers switch to their own.
- Validate it. Stores reject EPUBs that fail EPUBCheck: why your EPUB was rejected explains the common errors.
How do you format a PDF ebook?
A PDF is the opposite: the page is fixed, so the page is your job.
- Pick a page size and keep it. A4 or Letter suits a full-page guide or workbook read on a laptop or printed. A4, Letter or a trim size compares them.
- Start each chapter on a new page and keep headings with the text that follows them.
- Add page numbers, so readers can refer to a page.
- Embed the fonts, or the PDF looks wrong on someone else's machine: why your PDF looks wrong.
- Keep the file size down for email delivery: why your book PDF is 80 MB.
Do you need both formats?
Most authors who sell in more than one place do. A PDF for people who buy from you directly, and an EPUB for the stores and for buyers who read on a phone. EPUB or PDF goes through when each wins.
Making both from one source saves doing the work twice. In bukpress you write the book once in Markdown, and it exports a typeset A4 PDF and, on Pro, a reflowable EPUB 3 that carries the same fonts, colours and heading rules. Every # heading becomes a chapter in the EPUB's contents. The PDF is on every plan, including Free (up to 40 pages, 20 exports a month, no watermark); EPUB export is on Pro at $24 a month. See pricing and how the EPUB export works.
Common questions
What is the best ebook format?
EPUB, for anything sold through ebook stores. PDF, for anything you deliver yourself or expect people to print.
Is PDF an ebook format?
Yes, a fixed-layout one. It's the usual format for lead magnets and directly sold ebooks, but stores prefer EPUB because it reflows on small screens.
Can Kindles read EPUB?
Kindle apps and devices take EPUB through Send to Kindle, and KDP takes EPUB uploads. Amazon converts the file for Kindle.
How do I convert my ebook to another format?
Calibre converts between most ebook formats for free: Calibre covers what it does well. Converting a PDF to an EPUB rarely gives a good result: PDF to EPUB explains why.