What are EPUB and MOBI Files

EPUB and MOBI are file formats used to publish ebooks, books in a digital format that can be read on all kinds of devices. The major benefit of these file formats is their support for customization, allowing readers to change the font, font size, line spacing, and other elements to their liking, to attain a personally satisfying and enjoyable reading experience.

If you are deciding on an ebook format to use, it is best to choose EPUB for its wide compatibility with reading devices and software.

What is the EPUB file format

EPUB is a standard ebook file format maintained by the World Wide Web Consortium that can be read on many different devices and in many different software applications. It is the most widely used and supported ebook file format.
The EPUB file format supports many features, including both reflowable text and fixed-layout content, images (vector and raster), annotations, bookmarks, CSS, audio, and DRM. Though the file format supports all these features and more, their usability depends on their implementation in the devices and applications used to read them.

How do I read an EPUB file

On desktop and laptop computers

Desktop apps

Download and install one of the following apps to read EPUB files on your desktop or laptop:

• Calibre is a free, open-source ebook management solution and reader. It is available for Windows, MacOS, and Linux.
• Adobe Digital Editions is a free software available for Windows and MacOS.

Web browsers

Google Chrome, Mozilla Firefox, and Microsoft Edge have built-in support for reading EPUB files. These browsers and many others also have third-party extensions and plug-ins that provide EPUB-reading support.

On e-readers (Amazon Kindle, Barnes & Noble Nook, Kobo Libra, etc.)

Consult the documentation for your specific e-reader. Depending on your device, you may be able to add EPUB files to it via USB connection, WiFi, Bluetooth, email, or a special app or service from the manufacturer.

On phones and tablets (not e-readers)

• On iOS and iPadOS devices, use the Apple Books app.
• On Android devices, use the Google Play Books app.
• Many third-party ebook readers are available in the Apple App Store, Google Play, and Windows Store, and they support EPUB files. Some are built by reputable companies, like the Amazon Kindle app, while others may be projects built by hobbyists in their free time or by developers with malicious intentions. Use them at your own risk.

What is the MOBI file format

MOBI is a proprietary ebook file format that Amazon used as the basis for its Kindle File Format when the company debuted its Kindle devices in 2007. MOBI files support very basic typesetting and formatting. Even as Amazon advanced its Kindle File Format, ebooks outside of the Kindle Store were published and made available in MOBI format for its compatibility on both older and newer Kindle devices.
In December 2023, Amazon ended support for the MOBI format in the Send to Kindle service, which lets users add ebooks to their Kindle library via email, web upload, Kindle app, and Send to Kindle app. This change does not affect MOBI files already on users’ devices and does not prevent sideloading MOBI files on Kindles. Amazon encourages the use of EPUB files in place of MOBI files in its Send to Kindle service.

How do I read a MOBI file

On desktop and laptop computers

Desktop apps

Download and install one of the following apps to read MOBI files on your desktop or laptop:

• Kindle Previewer is built by Amazon for publishers to check out their ebooks before they are sent to the Kindle Store or devices. It is free and provides options for emulating different Kindle devices.
• The Kindle App can read MOBI files on PC and Mac.
• Calibre is a free, open-source ebook management solution and reader. It is available for Windows, MacOS, and Linux.

Web browsers

Some third-party extensions and plug-ins for web browsers are capable of reading MOBI files. Because the file format is no longer used by Amazon, these extensions are probably not actively maintained.

On Amazon Kindles

Maintain MOBI format

Use the Calibre desktop app or your OS’s file explorer to sideload the MOBI file on your Kindle via USB.

Change to another format

Use the Calibre desktop app to convert the MOBI file to any format supported by the Send to Kindle service, and then send the new file to your Kindle, or you can sideload the new file to your Kindle via USB through Calibre or your OS’s file explorer.

On non-Amazon e-readers, phones, and tablets

Use the converter built into the Calibre desktop app to convert the MOBI file to an ebook format supported by your device. After that, add the newly converted ebook file to your device as you would any other, whether that be via USB, email, WiFi, device-specific app, etc.