EPUB vs MOBI: Do You Still Need MOBI Files?

If you've read older self-publishing advice, you may think you need two ebook files: an EPUB for most stores and a MOBI for Kindle. That advice is now out of date, and following it can actually cause problems. Here's what changed and what you really need.

The Short Answer

You need an EPUB. You almost certainly don't need a MOBI. MOBI is a retired format, and Amazon itself no longer wants it for new books.

What EPUB Is

EPUB is the universal ebook standard. Apple Books, Kobo, Barnes & Noble, Google Play, and libraries all use it, and it's now the format Amazon prefers too. It's a reflowable format, which means the text adapts to any screen size and to the reader's chosen font and text size.

One good EPUB is the single file that works almost everywhere. That is why it's the format worth getting right.

What MOBI Was

MOBI was Amazon's old ebook format, used by early Kindle devices and software. For years, authors converted their EPUB into a MOBI to upload to Kindle, and tools produced MOBI files for exactly that reason.

The format is old, it has limitations compared with modern EPUB, and Amazon has moved on from it.

Amazon Now Takes EPUB

This is the key change. Amazon stopped accepting MOBI for new Kindle uploads, and Kindle Direct Publishing now takes EPUB directly. Behind the scenes, Amazon converts your EPUB into its own modern internal format for Kindle devices, but that is Amazon's job, not yours. You upload EPUB, and Kindle handles the rest.

You may still see references to formats like AZW3 or KFX. Those are Amazon's own internal Kindle formats, not something you create or upload. You don't need to produce them.

What You Actually Need Today

For almost every author publishing now, the answer is simple: create one well-made EPUB and use it everywhere, including Amazon. There's no need to make a separate MOBI, and no need to worry about Amazon's internal formats.

The only time you might still touch a MOBI is if you're dealing with a very old Kindle file from years ago, which is rare and not something new books need to think about.

How to Make a Good EPUB

Because the EPUB is now the one file that matters, it's worth making it properly, with a working linked table of contents, clean chapter structure, and valid markup that passes retailer checks. Koberger exports a validated EPUB (one that passes the file checks the stores themselves run) from your book project, so the file you upload to Amazon is the same one you upload to Apple Books, Kobo, and every other store. If you're new to the format, see how to create an EPUB file.

Bottom Line

MOBI is a relic. EPUB is the present and the future, and it's the only ebook file you need to publish today, Amazon included. Make one solid EPUB, upload it everywhere, and let the stores handle their own devices.