EPUB vs. MOBI vs. PDF: Which Format Do You Actually Need?

EPUB, MOBI, PDF, the alphabet soup of eBook formats confuses almost every new author. The good news: you probably need fewer of them than you think. Here’s what each format is actually built for, which one your retailers want in 2026, and how to stop worrying about MOBI (spoiler: it’s retired). By the end you’ll know exactly which files your book needs.

What Each Format Is Built For

• EPUB, the modern eBook standard. It’s reflowable: text adapts to any screen, font, and size. It’s what Apple Books, Kobo, Google Play Books, and Kindle all work with today.
• MOBI, Amazon’s original Kindle format. It’s been phased out: KDP stopped accepting MOBI uploads, and EPUB took its place. You almost certainly don’t need it anymore.
• PDF, a fixed, print-style format. Every element stays exactly where you put it. Great for paperbacks, hardcovers, workbooks, cookbooks, and anything where layout must not move, but rigid on small eBook screens.

Which Retailers Require Which Format

The pattern is clear: EPUB for e-books, PDF for print. MOBI doesn’t appear, because it’s no longer used. (For the print PDF rules, see our KDP formatting checklist.)

Reflowable vs. Fixed-Layout Formatting

This is the decision that actually matters, more than the file extension:

• Reflowable (EPUB): text flows to fit the device and the reader’s chosen font size. Best for novels, most nonfiction, memoirs, anything text-driven. It’s what readers expect on e-readers and phones.
• Fixed-layout (PDF, or fixed-layout EPUB): the page looks identical everywhere. Necessary for children’s picture books, cookbooks, photography books, and complex textbooks where design and text must stay together, but a frustrating read at small sizes.

Choose based on your book’s content, not habit: a novel should reflow; a heavily designed book may need fixed layout. (Your cover follows the same logic, see eBook vs. print cover specs.)

So Which Formats Do You Actually Need?

For the vast majority of authors, the answer is simple:

• ✅ EPUB, for every e-book retailer (Kindle, Apple, Kobo, Google).
• ✅ Print-ready PDF, for your paperback and/or hardcover.
• ❌ MOBI, not needed; it’s retired.
• ➕ Fixed-layout EPUB, only if your book is design-heavy (picture book, cookbook).

That’s it. Two files cover almost everyone. The work isn’t collecting formats, it’s producing each one correctly so it displays properly everywhere.

How Prime Publishing Hub Helps

Prime Publishing Hub’s formatting service delivers all the formats your book actually needs, a clean, reflowable EPUB for e-book retailers and a print-ready PDF for print, in one coordinated package, so you’re never stuck converting files or troubleshooting broken layouts on a Kindle.

Want every format done right? Request a free quote or talk to our formatting team.