EPUB vs mobi: Is Amazon's mobi Format Now Dead?

For over a decade, self-publishing authors who were looking to distribute their ebooks with major retailers had two different ebook formats to manage: EPUB files and mobi files. But with recent developments on Kindle Direct Publishing (KDP), Amazon’s author publishing platform, most indie authors now only have to deal with one format: the EPUB.

In this post, you’ll learn about the most popular ebook format — and why it's probably the only one you need to know.

What is an EPUB?

An EPUB file is the most widely accepted ebook format on the market. It’s the industry standard, used by Apple, Kobo, Barnes & Noble, Sony, and Google e-readers. A free and open standard based on HTML (much like the files your web browser would read), EPUB is a flexible format that supports a wealth of features. It can:

• optimize a book’s text to fit your device;
• embed images;
• allow for bookmarking, highlighting, and text-to-speak.

The latest version, EPUB 3, will even permit you to add multimedia content like video and audio clips.

All things considered, it’s a pretty great format — which is why the publishing industry has rallied around it as its ebook format of choice.

What is a mobi file?

Mobi files were the ebook files used exclusively by Amazon’s Kindle devices. Well, for the last few years of its life, the actual proprietary standard was called AZW (or AZW3 or KFX, depending on the generation). 

Amazon is the largest ebook retailer in the world by quite a long way: in 2015, they were responsible for over 70% of ebooks sold in the US. This massive market share was part of why they could insist on using their own format for such a long time.

As of 2022, Amazon discontinued its use of the AZN and MOBI formats, encouraging users to upload EPUB files to KDP.

Top Tip: To make sure that your book looks just right before you start selling it on Amazon, you can upload and validate your EPUB using Amazon's own Kindle Previewer tool.

Is the mobi format now dead?

Pretty much! As of mid-2022, the format has joined the choir invisible. Any MOBI files previously uploaded to KDP are still safe, however — so no need to worry about that just yet.

When should you use PDF files?

The PDF, which has remained one of the most popular document formats since its debut in 2001, is still widely used in publishing for two purposes.

Print on Demand

Perhaps the most cost-effective way of selling physical copies on a small scale, self-publishing authors commonly use what’s called a print-on-demand (POD) service. Instead of ordering a print run and filling a warehouse with paperbacks, copies will only be printed as and when they’ve been purchased either by individual buyers or a bookshop.

The two most popular POD services are IngramSpark and KDP Print (formerly CreateSpace), the latter of which is — would you believe it? — an Amazon company.

For this, you will need a file that contains strict definitions of your book’s layout and content – which is why we use PDF files. There are countless different types of PDF out there but for our purposes, the format will need to a ‘print-ready PDF’ to make it compatible with printers.  Any hyperlinks will be removed and your image colors will be expressed in CMYK, and not using the RGB color model.

Graphically Intensive eBooks

Both EPUBs and mobis are great at handling text-intensive books like novels, memoirs and some non-fiction books. They are, however, less awesome at dealing with books that have a lot of images, graphs and photos — art books and travel guides, for example. If you need your ebook to look exactly the same as the print version, you may wish to sell it as a PDF, which will ensure fidelity across all devices.

The downside is that basic black-and-white Kindles (and e-readers like it) will struggle to display them well — as these PDF books will tend to be fixed-width. Unlike an EPUB file, where the text is "reflowable" and will adapt to the shape and size of your device, reading a small-print PDF book on a Kindle Paperwhite is nothing short of a chore.

Creating EPUBs and print-ready PDFs

Reedsy offers a free online book editing tool that lets you professionally format a book with no training required. Once you’re happy with how it looks, you can export your book for free as both EPUB and print-ready PDF files!

To find out more about how the Reedsy Studio can help you publish your own book, click here.

To learn more about how to set up your ebook on the different retailers, read our master guide on ebook publishing platforms.

[updated: 11/03/2020 UTC]