Introduction
In the digital publishing world, choosing the right eBook format is just as important as the content itself. Whether you’re an author, publisher, marketer, or educator, the format you select directly impacts how readers experience your eBook—across devices, platforms, and apps. Among the many file types available, EPUB, PDF, and MOBI are the most commonly used and often the most debated.
Each format has unique strengths and limitations. EPUB offers flexibility and reflowable text, making it ideal for most modern eReaders. PDF is beloved for its fixed layout and universal accessibility. MOBI, once dominant thanks to Amazon Kindle, is now being phased out in favor of Kindle’s newer formats. But the truth is, there’s no one-size-fits-all answer—the best format depends on your goals, your audience, and your distribution platform.
In this guide, we’ll break down these three popular eBook formats in detail—how they work, what they’re best for, and how to decide which one is right for you.
What Is EPUB?
EPUB (Electronic Publication) is an open standard for eBooks developed by the International Digital Publishing Forum (IDPF). It is widely supported by most non-Amazon eReaders, including Apple Books, Google Play Books, Kobo, and Nook. One of EPUB’s key strengths is its reflowable content, meaning the text automatically adjusts to fit the screen size of the device, enhancing readability across smartphones, tablets, and eReaders.
Key Features of EPUB:
- Reflowable text: Enhances readability on all screen sizes.
- Interactive content: Supports audio, video, hyperlinks, and animations.
- Open standard: Can be used and modified without licensing fees.
- Widely supported: Compatible with nearly every major platform except Amazon Kindle (without conversion).
EPUB is ideal for most eBooks that are primarily text-based—such as novels, non-fiction, and guides. It offers excellent flexibility and accessibility, especially when reaching a global, device-diverse audience.
However, EPUB is not always suitable for documents that require fixed layouts, such as heavily designed PDFs or image-driven books (cookbooks, comics, etc.), unless advanced layout features (like EPUB3) are used.
What Is PDF?
PDF (Portable Document Format) is a format developed by Adobe to present documents consistently, regardless of hardware, software, or operating system. Unlike EPUB, PDF uses a fixed-layout structure, meaning the formatting remains identical no matter the screen size or device. This makes it perfect for preserving the exact look of documents, including fonts, spacing, images, and colors.
Key Features of PDF:
- Fixed layout: Ensures precise visual consistency across all devices.
- Universal compatibility: Can be opened on nearly any device with a PDF reader.
- Supports rich media: Images, graphs, hyperlinks, and interactive forms.
- Print-friendly: Ideal for downloadable print versions or printable worksheets.
PDF is a popular choice for business documents, workbooks, whitepapers, academic resources, and marketing materials. It’s also widely used for free eBook downloads and lead magnets because of its accessibility and ease of distribution.
However, its fixed layout can be problematic on small screens like smartphones, requiring users to zoom and scroll horizontally to read the text—creating a poor mobile experience compared to EPUB or MOBI.
What Is MOBI?
MOBI is a format that originated with Mobipocket Reader software and was later adopted by Amazon for its Kindle devices. While Amazon has transitioned to AZW and KPF (Kindle Package Format) for Kindle publishing, MOBI remains important for legacy support and offline eBook sharing.
Key Features of MOBI:
- Reflowable text: Similar to EPUB, adjusts to screen size.
- Used by Kindle devices: Once the primary format for Amazon Kindle.
- Smaller file size: Optimized for fast downloads and lower storage usage.
- Limited support for rich media: Not ideal for interactive or image-heavy content.
MOBI is still accepted by many third-party platforms for Kindle compatibility, but Amazon now recommends uploading eBooks in EPUB or DOCX formats and automatically converts them to KPF during the Kindle publishing process.
If you’re self-publishing on Kindle Direct Publishing (KDP), there’s no need to manually create MOBI files anymore. Kindle Create or KDP’s built-in converter handles that for you.
Comparison Table: EPUB vs. PDF vs. MOBI
| Feature | EPUB | MOBI | |
|---|---|---|---|
| Text Flow | Reflowable | Fixed layout | Reflowable |
| Device Compatibility | Most devices except Kindle | All devices | Kindle devices |
| Interactive Content | Yes (EPUB3) | Limited | Limited |
| Print Support | Not ideal | Excellent | Not designed for print |
| Editing Flexibility | Moderate | Difficult to edit | Limited |
| Best Use Case | Novels, guides, how-to books | Workbooks, printables | Kindle publishing (legacy) |
| File Size | Small to moderate | Usually larger | Small |
| Market Reach | Wide (non-Amazon platforms) | Broad (easy to email/share) | Amazon Kindle-specific |
Which Format Is Best for You?
If You’re a Self-Publishing Author…
For most self-publishing authors, EPUB is the go-to format—especially if you want your book to be available across various platforms. It ensures your text adapts beautifully to different screen sizes, making it a seamless reading experience.
However, if you’re publishing exclusively through Amazon’s Kindle Direct Publishing, you don’t need to create MOBI yourself. Instead, upload an EPUB or DOCX file, and KDP will handle the conversion for Kindle.
If you’re offering sample chapters, bonus content, or downloadable guides on your website, PDF is a great format for quick downloads, especially if the document includes graphics or layout-heavy elements.
If You’re Creating Marketing or Educational Materials…
PDF is hard to beat for lead magnets, checklists, and instructional guides. Its fixed format ensures that your content looks polished, whether printed or viewed on a desktop. For mobile viewing, keep formatting clean and use larger fonts to improve readability.
EPUB can also be used for digital guides, especially when targeting readers who prefer to consume content on eReaders like Kobo or Apple Books. However, you’ll need a compatible app or software to create and preview EPUB documents effectively.
If Your Focus Is Amazon Kindle…
Though MOBI was once essential, EPUB is now preferred by Amazon, and KDP will convert your uploaded EPUB file into Kindle-compatible format. Tools like Kindle Create simplify this process, letting you preview and format your eBook before publishing.
For authors distributing outside of Amazon, MOBI can still be used for sending ARC (Advance Review Copy) files to readers with older Kindle devices. But for long-term publishing, focus on EPUB and PDF.
Creating and Converting eBook Formats
Here are some of the most popular tools to help you create and convert between EPUB, PDF, and MOBI formats:
- Calibre (Free): A powerful open-source eBook manager that can convert between EPUB, MOBI, PDF, and more.
- Kindle Create (Free): Amazon’s official tool to format your manuscript for Kindle.
- Adobe InDesign (Paid): Great for exporting fixed-layout eBooks and PDFs.
- Reedsy Book Editor (Free): Create beautifully formatted EPUB and PDF files.
- Canva (Free/Paid): Useful for creating workbooks and PDFs with rich visuals.
- Scrivener (Paid): For authors writing long-form content; export to EPUB and PDF.
Tips for Choosing the Right Format
- Know Your Audience: Are your readers mostly Kindle users? iPad users? Do they prefer print-friendly downloads or interactive reading experiences?
- Match the Format to the Content: Simple text-based books work best in EPUB, whereas image-rich documents or complex layouts are better suited for PDF.
- Think About Distribution: If you’re using multiple platforms (Amazon, Kobo, Google Books, Apple Books), you’ll need at least an EPUB. If you’re only sharing via email or on your website, a well-designed PDF may be sufficient.
- Plan for the Future: MOBI is being phased out. Focus on EPUB and PDF for long-term compatibility and reader satisfaction.
Conclusion
Choosing between EPUB, PDF, and MOBI doesn’t have to be confusing—it simply requires a clear understanding of your goals, your audience, and how your eBook will be used. EPUB is the most flexible and modern format, offering an adaptive reading experience across a range of devices. PDF, while not ideal for mobile, remains an excellent choice for printable resources and visually consistent documents. MOBI is increasingly obsolete but still relevant for older Kindle users and certain niche cases.
In most situations, authors and content creators benefit from offering their eBooks in multiple formats to cater to various preferences and devices. Luckily, with today’s tools, converting between formats is easier than ever.
Whether you’re publishing your first eBook or managing a digital content library, understanding these formats will ensure that your message is delivered just the way you intended—clear, accessible, and professional.
