For those authors and publishers who have debated the difference between using EPUB or Mobi formats for ebooks, or possibly paid for both, change is coming.

Mobi was traditionally the proprietary format for Amazon Kindle. Given that’s where the huge majority of ebooks are sold, having your ebooks on Amazon Kindle was critical for most authors and, as a result, so was the Mobi format.

EPUB was the format that was used everywhere else.

However, from June 28, 2021, Amazon Kindle will be retiring the Mobi format. An EPUB file will be acceptable instead.

The debate between which was best is over by default, and the history of these formats will be written by the victors (and published as an ebook in EPUB).