Amazon has long been the odd man out in the world of ebook files for their requirement of MOBI files. All other platforms use EPUB. But yesterday, Amazon sent out emails to authors to let them know that they have finally listened: to simplify the uploading process, they will begin using EPUB files on June 28, 2021. You won’t have to worry about changing your existing files, unless you upload a new version, but for all new books and any updates, you’ll want to make sure you have an EPUB handy.
What Happens on the Kindle Side
Even though Amazon is now only accepting EPUB files, Amazon will still be delivering MOBI files to Kindles. This means that the EPUB file will be converted by Amazon on the backend into a MOBI file. Because of this conversion, it’s important to double-check your ebook in Kindle Previewer 3 to be sure everything looks correct after it is converted.
For support, please visit Kindle direct publishing or KDP.