EPUB vs MOBI vs PDF: which is the best eBook format?

What is EPUB?

EPUB stands for Electronic Publication; files designed store and read eBooks. They’re also ‘open standard’, meaning EPUBs aren’t company-owned and are widely compatible with different eBook readers.

EPUBs are also ‘reflowable’, meaning they automatically reformat content to your screen and device. To accomplish this, readers can change the font size, style, and spacing of an EPUB, making it convenient to use across various devices, like phones and tablets.

The flexibility EPUBs offer is one of the reasons for their popularity in eBooks. EPUBs are programmed with HTML and CSS, like web pages. This allows for compatibility with various components such as text and images.

For more information, check out our EPUBs guide.

EPUB pros and cons.

EPUB has become an industry-standard format in the world of digital publishing, especially for fiction and text-based content. Its design is built for adaptability, rather than a fixed, rigid structure. Understanding the benefits and drawbacks can help you decide if they’re right for you.

Pros.

• Wide compatibility. Works on most eReaders and apps, such as Apple Books, Kobo, and Adobe Digital Editions.

• Reflowable format. Adjusts the text to automatically fit the screen, which improves readability and reduces the need for manual adjustment.

• Supports multimedia. Can include images, tables, and basic interactive elements, like menus.

• Customisable reading experience. Readers have full control over font size, type, and line spacing.

• Open standard. Not owned by a single company, making it more accessible.

Cons.

• May not support complex layouts. EPUB can have difficulty with fixed-format content, such as magazines and textbooks.

• Security risks. Doesn’t have DRM (Digital Rights Management) protection, making it more susceptible to copying, modifying, and sharing without permission.

• Not natively supported by Amazon Kindle. They require conversion before use on Kindles.

What is MOBI?

MOBI refers to a MobiPocket eBook format – an eBook format originally developed for reading digital books on mobile devices. This format has become synonymous with Amazon Kindle, as it was used on their devices for many years. MOBI also supports features such as bookmarks and annotations.

However, MOBI use has declined in recent years as Amazon has moved towards new formats, such as AZW. This change has contributed to MOBI becoming almost obsolete, as it’s rarely used these days.

Learn more about MOBI files.

MOBI pros and cons.

MOBI files played an important role in the eBook boom that popularised the transition from traditional paper books to eBook readers. It reflects the technical limitations and habits of that era, which prioritised efficiency and basic functionality over enhanced display features. But it was a trailblazer – a first ‘raw’ model which paved the way for further advancements.

Pros.

• Reflowable text. Adapts content to different screen sizes for better readability.

• Simple to publish. Easy to upload and distribute via Amazon Kindle Direct Publishing.

• Lightweight format. Small file size makes it fast to download and load on devices.

• Supports basic interactivity: Handles bookmarks, annotations, and simple hyperlinks.

Cons.

• Compatibility issues. Limited support on non-Kindle devices and eReader apps.

• Limited font capabilities. Not ideal for complex designs or multimedia-heavy eBooks.

• Outdated format. Amazon replaced MOBI with newer formats.

• Limited styling options: Less flexibility compared with EPUB for advanced formatting.

What is a PDF?

PDF stands for Portable Document Format – a format that makes it easy to share and present documents consistently across various devices. PDFs are slightly different from eBook and Kindle file formats, as they preserve the original layout and content styling, so they appear the same regardless of the devices they appear on.

They’re ideal for magazines, brochures, manuals, and business documents, which place greater emphasis on the fixed element of the design. They’re widely supported by various software and many web browsers, with hyperlinking, forms, and annotations easily supported. PDFs are ideal for students, professionals, freelancers, and anyone who has content to present in its true style.

Want to know more? Discover all you need to know about PDFs.

PDF pros and cons.

Imagine you have a CV and need it to apply to that great job role you’ve seen. What do you think looks better – sending it as a Word document or a fixed PDF?

PDF looks ‘tidier’ and more professional. They’re also harder to edit or tamper with, which is better for presentation and safeguarding personal information. Like anything, they have their pros and cons too.

Pros.

• Strong compatibility. Works on multiple devices.

• Fixed layouts. Preserves original content formatting.

• Easy to protect and secure. Can restrict their access with PDF password protection.

• Supports multimedia and interactivity. Easy to embed hyperlinks and forms.

• Professional presentation. Ideal for reports, manuals, and brochures.

Cons.

• Not always editable. Editing PDF content seamlessly often requires the use of specialist tools and software, like Adobe Acrobat Pro.

• Large file sizes. File sizes can be large .

• Limited reflow on small screens: Fixed layout can make reading on mobile devices harder.

• Less flexible for eBooks: Not ideal for adjustable text or interactive reading features.

Find out how to convert a PDF to use on Kindle with our handy guide.

When should you use an EPUB, MOBI or PDF file?

There’s no one-size-fits-all answer on which you should use. It all depends on what you’re using it for and how you wish to deliver the content to your audience. You’ll also need to consider what devices the content will be used on, and whether customisation and flexibility are important.

Below are some common uses for each file type. Compare EPUB vs MOBI vs PDF and decide which one’s best for you.

When to use EPUB files.

• When you want something to feel like a digital book, not just a scanned document.

• Long-form reading, such as fiction and narrative-based pieces, works best with adjustable, reflowable text.

• Compatible with various platforms.

• Small file sizes support basic imagery, navigation, and some multimedia.

When to use MOBI files.

• If you or your audience still rely on older Kindle and eReader models that use MOBI.

• For older books or documents that are already packaged as MOBI, it may be tricky to convert.

• As a transitional option when preparing content for older Kindle devices. But please note, Kindle doesn’t favour MOBIs much these days, making it less ‘future proof’.

When to use PDF files.

You should consider using PDF files in the following circumstances:

• When maintaining a controlled design is more important than flexible text. For instance, when sharing and viewing company brochures.

• For textbooks, instruction manuals, contracts, and datasheets (such as end-of-year financial reports), where accurate printing is crucial. When formatted as a PDF, you can also annotate these documents – ideal for collaboration and feedback.

• When you need documents that are easy to reorder, so you can collate different pages, or remove sections as a separate document.

FAQs.

What is the key difference between EPUB, MOBI, and PDF?

The main difference between EPUB, MOBI, and PDF is reading flexibility. EPUB and MOBI have adjustable (reflowable) text, which automatically fits to any screen, regardless of its size or orientation. PDF documents, on the other hand, provide a fixed layout that preserves the original dimensions and design.

Is EPUB better than PDF?

Whether EPUB is a better choice than PDF depends on the purpose and intent of your document. EPUB works best on eBook reading devices, whereas PDFs can be used on any device. Neither is ‘better’. It comes down to compatibility and how you want readers to interact with the document.

Can EPUB be trusted?

EPUB files themselves, by their nature, are safe. Whether each file is trustworthy comes down to who the provider is, i.e., where are you getting it from? It’s not the file type, but the file’s source that’s important for safety. Make sure to vet the document provider before downloading it, as EPUBs function much like a ZIP file.

More useful resources.

• Kindle formats explained.

• How to convert EPUB to MOBI.

• How to convert MOBI to EPUB.

• How to convert EPUB to Kindle.

Adobe Acrobat has all the tools you need to help you use PDFs your own way. Make PDFs your own with Adobe Acrobat.