PUB vs. MOBI vs. PDF: Which Format Is Right for You?

When preparing your book for digital publishing or Amazon KDP, one of the first decisions you’ll make is choosing the correct file format. Understanding the difference between EPUB, MOBI, and PDF is essential if you want your book to display correctly on all devices, look professional, and provide a smooth reading experience for your audience. Each format serves a different purpose, and choosing the right one can significantly impact how readers interact with your work.

What Are the Main eBook Formats?

Before deciding which file type to use, it’s helpful to understand how each format behaves and where it works best.

• EPUB is the universal eBook format used by most digital bookstores.

• MOBI was Amazon’s older Kindle format and is now mostly outdated.

• PDF is a fixed-layout format ideal for design-heavy and print-ready books.

These three options cover nearly every type of publishing scenario, from flexible reflowable eBooks to precise print layouts.

EPUB: The Most Flexible and Widely Supported Format

EPUB (Electronic Publication) is the most commonly used format across modern digital reading platforms. It’s perfect for authors who want to create a smooth, adjustable reading experience where text can shift and resize depending on the reader’s device. This makes it ideal for Kindle uploads, Apple Books, Google Play Books, and any platform that supports reflowable eBooks.

EPUB works particularly well for novels, chapter books, and nonfiction titles where the reading experience should feel natural across phones, tablets, and e-readers. Because it supports adjustable fonts, clean formatting, clickable links, and lightweight file sizes, many authors choose EPUB when they want their book to feel like a true digital reading experience.

However, EPUB isn’t the best choice for books that rely on precise layouts. If your book needs the images, text, and backgrounds to remain in exact positions—such as in children’s picture books or activity books—this format may not preserve the layout the way you expect.

MOBI: Amazon’s Legacy Format for Older Kindle Devices

For many years, MOBI was the only way to publish a Kindle eBook. Today, Amazon has fully transitioned to accepting EPUB uploads and converting them into its modern KPF format. This means MOBI is no longer needed for KDP publishing and should not be used for uploading new eBooks.

MOBI still has a small purpose: some authors use it to send preview copies to beta readers who own older e-readers or for testing how a file looks on legacy Kindle devices. Beyond this, its limitations—such as outdated formatting capabilities and limited support—make it impractical for today’s publishing standards.

If your goal is to create a professional, modern Kindle eBook, EPUB is now the format Amazon recommends.

PDF: The Best Option for Print-Ready Books and Illustration-Heavy Layouts

PDF remains the gold standard for books that depend on exact, unchanging page layouts. This makes it the absolute best format for children’s picture books, activity books, coloring books, graphic novels, cookbooks, and any title where the design matters just as much as the text.

A PDF preserves every detail of your layout—including images, typography, backgrounds, and spacing—so your book prints exactly the way you designed it. Because Amazon KDP requires a print-ready PDF for all paperback and hardcover interiors, it’s the format authors rely on for high-quality printing.

However, PDFs are not ideal for reading on small screens. Since the text cannot reflow or adjust, readers must zoom and pan, which is uncomfortable for phone or Kindle reading. For this reason, most authors use PDF for the print version and EPUB for the Kindle version of the same book.

Which Format Should You Choose for Your Book?

The right format depends entirely on the type of book you’re creating and where you plan to publish it.

Choose EPUB if:

• Your book is primarily text, such as a novel, chapter book, or nonfiction guide.

• You want your book to work on all major eReaders, including Kindle, Kobo, and Apple Books.

• You want adjustable text that gives readers full control over their reading experience.

• You are publishing a Kindle eBook that doesn’t require fixed illustrations.

Choose PDF if:

• You’re publishing a children’s picture book with full-page illustrations.

• Your book includes detailed layouts, charts, or artwork.

• You want a professional print-ready file for Amazon KDP.

• You need complete control over margins, bleed, image alignment, and design.

Use MOBI only if:

• You are sending preview copies to readers with older Kindle devices.

• You are testing how your book appears on legacy Kindle hardware.

In nearly all modern publishing cases, EPUB and PDF are the formats authors rely on.

Quick Comparison of EPUB, MOBI, and PDF

• EPUB offers flexible, reflowable text and is ideal for digital reading on any device.

• MOBI is now outdated and no longer accepted for Kindle publishing, useful only for testing.

• PDF provides a fixed layout, perfect for illustration-heavy books and print interiors.

Each format plays a different role in the publishing process, and choosing the correct one ensures your readers enjoy a smooth, professional experience—whether they’re reading on a Kindle or flipping through a beautifully printed picture book.

Final Thoughts

Deciding between EPUB, MOBI, and PDF depends on your publishing goals, your book’s design needs, and the reading experience you want to deliver. EPUB is ideal for digital reading, PDF is essential for print-ready and illustration-centered books, and MOBI serves only niche purposes today.

If you need help converting your book into the right format—or want professional assistance with formatting, layout, illustration, or KDP preparation—Whimsy Studios can guide you through every step of the process.

Visit WhimsyStudios.net to get expert support for your next book.