It’s Time for Kindles to Natively Support EPUB

Arvyn Cerézo

Senior Contributor

Arvyn Cerézo is an arts and culture writer/reporter with bylines in Book Riot, Publishers Weekly, South China Morning Post, PhilSTAR Life, the Asian Review of Books, and other publications. You can find them on and @ArvynCerezo on Twitter.

The inner workings of the ebook world may feel strange and trivial to the average reader, but knowing how things work behind the scenes may help elevate our reading lifestyles, such as helping us decide between Kindle or Kobo ereaders, warning us how difficult it is to migrate our digital library, or helping us decide whether to download an EPUB or a MOBI file.

In 2005, Amazon purchased Mobipocket and eventually adopted MOBI, its file format, instead of EPUB, for its Kindle devices when they were released in 2007.

At the same time, EPUB was released in 2007 and is still being supported today, adding features that are superior to MOBI. On the other hand, when Amazon acquired MOBI, the quality went downhill. Then the software, as well as the file format, was eventually phased out. It’s still being discontinued at the moment as Amazon now focuses its energy on AZW3, a resurrected version of MOBI.

As MOBI fell out of favor, EPUB took its place as the industry standard. Except for Amazon, almost all ebook vendors prefer to use it. Since it’s a universal file format, every company that deals with ebooks should employ it, just as the smartphone industry is transitioning to USB-C to standardize charging cables.

With MOBI’s downfall, Amazon will no longer fully support it in any Kindle system before the year ends, as Send to Kindle for MOBI will no longer work. Amazon now favors EPUB, slowly integrating it into its ecosystem. When you sideload an EPUB file on a Kindle device (which you could not before), however, the file is converted into AZW3.

Why is it so difficult for Amazon to simply support EPUB natively?

Standardizing Ebook Formats

Because EPUB is a universal file format, it can be read by any ebook reading system, including Apple, Google Play, Barnes & Noble’s Nook, and others. There are active developments that support it and create and maintain standards, such as the International Digital Publishing Forum. There are organizations that build it and monitor its progress, such as W3, which then merged with IDPF. If a file format is being actively developed by governing bodies, it can withstand changes in the industry.

As an ebook developer, I find that EPUBs are easier to fix than proprietary formats such as AZW3 or MOBI. I can break apart an EPUB file using existing software, whereas proprietary formats are impossible to troubleshoot because of their close-door nature.

Furthermore, converting EPUB to AZW3 with a Kindle device is not without flaws. Some readers have reported problems with it, claiming that the end result is poorly formatted. Although there are workarounds, the average reader who lacks technological knowledge would be unable to figure it out for themselves. This results in an underwhelming user and reading experience.

Some people also claim that when they sideload EPUB files to a Kindle, the cover disappears. Some users have problems with the table of contents, and some EPUBs become documents on a Kindle. It also appears to have issues with foreign-language books.

Amazon’s approach is clearly not ideal. So, rather than avoiding it, why not support EPUB natively?

Why Amazon Pivots Toward EPUB Support

Perhaps the main reason is that EPUB is currently not supported by any Kindle devices. However, Amazon could very well do so in the future for new releases and upgrades. The company has nigh unlimited resources, and it has the ability to overhaul its reading ecosystem if it so desires, but it chooses to build a walled garden around Kindle and make it difficult for ebook readers to use devices that truly support EPUB files. I believe that Amazon wants readers to use proprietary formats to further integrate them into the Kindle ecosystem.

Amazon may want EPUB readers to continue using Kindle devices, enticing them with its conversion feature so readers would continue to be in the Amazon ecosystem. If readers upload their EPUBs on their Kindle, readers will see advertisements to purchase ebooks. Eventually, Kindle will become their preferred ereader device. Because, well, why not? Amazon supports EPUB now (kind of!). However, they’re unaware of the lingering effects of this.

As a result, Amazon gets the last laugh by attracting more readers and customers from other retailers, resulting in more market dominance.

The way in is very easy, but the way out is not.

Amazon’s support for EPUB is long overdue, but it should be implemented properly. If it truly wants to be useful to ebook readers, it should support EPUB natively and stop holding on to AZW3. There should be a way out, not just in, so that ebook readers aren’t left trapped in the Kindle ecosystem if they change their minds. Sideloading EPUBs to Kindle converts them into AZW3s, effectively locking readers in. What happens if they want to move their entire digital library to Kobo? Those hundreds of AZW3s are unreadable in either a Kobo or an iPad. A backup of EPUB files would easily solve the problem, but I can only hope all readers are so diligent.

For the ebook industry to thrive — and for people to be encouraged to read more — ecosystems such as Kindle must stop constructing walled gardens and instead make file formats accessible and pleasantly readable to all ereaders.

It’s past time to abandon proprietary file formats in favor of the widely used EPUB. Allow people to transfer their digital library to any ereader they want. Instead of only letting people in, give them a way out.