What is the Best eBook File Format?

Jul 09, 2024
10 min
Best eBook File Format

Choosing the right eBook format makes your reading experience better in several ways. It improves readability, ensures compatibility with your devices, offers interactive features, and optimizes file size.

However, with so many formats to choose from, it can be challenging to decide which one is best for you. In this guide, we’ll highlight the most popular digital book formats to make your choice easier. By learning what each format has to offer and where it might fall short, you can make smarter decisions that ensure your eBooks are easy to read and navigate.


Many consider EPUB the best eBook format because it's flexible and compatible with many eReaders, including Amazon Kindle, Apple and Android devices, as well as Rakuten Kobo. It is reflowable, which means that it adjusts text and images to fit any screen size, making it perfect for reading on smartphones, tablets, and eReaders.

The EPUB format supports multimedia and interactive content, enhancing the reading experience beyond plain text. As an open standard, it is free from proprietary restrictions, so it works with many devices and apps like Calibre and Apple Books.

Our platform has its own online PDF to EPUB converter for Mac, Windows, and Linux. You can use it to make your PDF eBooks reflowable and more convenient to read. Whichever format you need to convert, PDF Guru has you covered.


iBooks is a proprietary file format based on EPUB, designed specifically for Apple iOS devices, including computers, laptops, phones, and tablets. This adaptable format is ideal for creating interactive, multimedia-rich eBooks, as it supports various types of media such as text, videos, presentations, images, and even 3D objects.

A standout feature of iBooks is the iBooks Author tool, which allows authors to design and publish their eBooks for free. However, it's worth noting that iBooks files can only be converted to the iBooks format, PDF files, or plain text files. A standout feature of iBooks is the iBooks Author tool, which lets authors design and publish their eBooks for free.


However, this isn't always a good thing since most eBook readers have fairly small screens and most PDF files contain text in small font size, making it uncomfortable to read. For these cases, you can use our online PDF converter to turn your PDFs into something more manageable like EPUB files.

On a positive note, PDFs can handle various types of content, from text and images to multimedia elements like videos and interactive forms. They also support features like annotations, digital signatures, and encryption, making them suitable for both casual reading and professional use. Additionally, interactive PDFs can include features such as clickable links, form fields, and embedded multimedia, providing a more engaging reading experience.

digital book formats


MOBI used to be the standard file format for Amazon Kindle devices. However, in recent years, it has been gradually becoming obsolete. In August 2022, Amazon officially retired the MOBI format and replaced it with EPUB, which is now the universal file extension for eBooks. You can still open MOBI files using compatible eReaders or convert them to a more up-to-date format.

We suggest converting MOBI to PDF or EPUB to preserve them and ensure stability. This will ensure compatibility with Kindle devices and allow you to benefit from the latest features and support.

AZW and AZW3

AZW and AZW3 are eBook formats created by Amazon for Kindle devices. They enhance the reading experience with features like bookmarks, annotations, and multimedia content. AZW3, also known as Kindle Format 8 (KF8), offers more advanced formatting capabilities than the original AZW. Both formats are protected by DRM (Digital Rights Management) to prevent unauthorized copying.

Although these formats are mainly designed for Kindle, they can also be accessed on other platforms using the Kindle app. However, to ensure broader compatibility, it's often a good idea to turn AZW and AZW3 files into more universal formats like EPUB or PDF. If you decide to stick with AZW3, you can easily convert PDF files to AZW3 using our online tool.

Comic book formats: CBR (RAR) and CBZ (ZIP)

CBR (Comic Book RAR) and CBZ (Comic Book ZIP) are the most popular formats for digital comic books. These formats contain a sequence of image files, usually in JPG or PNG format, representing the pages of a comic book. The main distinction is the compression method: CBR uses RAR compression, while CBZ uses ZIP.

Both formats allow comic book pages to be stored and viewed as a single file, making it easy to manage and read comics. They are widely supported by various comic book reader applications, ensuring users can enjoy comics on multiple devices.

How to choose the right eBook format

For eBooks that include visuals or require a specific layout, PDF or fixed-layout EPUB are more suitable. PDFs are universally accessible but not reflowable, making them less ideal for smaller screens, whereas AZW3 and EPUB files maintain the design integrity across devices.

FormatsPlatformsFixed layoutInteractivityDRM protectionDirect Print
All except old Kindles

ebook file types

What other file formats can be used for eBooks?


A DjVu file is a scanned document saved in the DjVu image format. Once considered a promising alternative to PDF for storing content, DjVu offered highly compressed file sizes compared to PDF at the time. However, PDF has since become the universal standard for electronic documents, and DjVu is gradually becoming obsolete.

There are still many DjVu eBooks available on the internet, but as the format becomes less supported, users may struggle to access and read these documents. Converting DjVu to PDF, which is a more widely format, can help ensure better compatibility and a smoother reading experience across various devices.


RTF is a Microsoft-developed file format that allows for basic text formatting and supports embedding images. Though it’s not the preferred choice for eBooks due to its limited advanced features and inconsistent support, its simplicity and broad compatibility make it useful for some basic purposes.


TXT files are among the simplest eBook formats, designed solely for textual content without support for images or graphs. They are perfect for text-heavy eBooks like research reports due to their simple nature and compatibility with basic fonts and styles. Although they don't have features like security protection, fixed layouts, or interactive elements, their simplicity makes them an accessible choice for text-only publications.

Ultimately, choosing the right file type for an eBook depends on your specific needs and preferences. Think about the type of content you usually consume — whether it's mostly text-based, illustrated, or interactive — and then consider which devices you will view it on. With these factors in mind, choose a format that offers the best reading experience.