MOBI format
MOBI is an ebook format that came from Mobipocket, a company Amazon bought in 2005, and early Kindle devices were built around it. For years, self-publishers produced MOBI files to upload to Amazon or to send to readers’ Kindles. Amazon has since moved to newer Kindle formats, such as AZW3 and KFX, which it generates itself from the files authors upload.
Today MOBI is a legacy format. KDP no longer accepts MOBI files for ebook uploads: it stopped taking them for reflowable ebooks in 2021 and later for fixed-layout ones. Instead, KDP takes EPUB, the preferred format for most books, as well as Word (DOCX) files and KPF files from Kindle Create. Amazon’s Send to Kindle service has also dropped MOBI in favor of EPUB.
Why it matters for indie authors
If a guide, template or conversion tool tells you to “make a MOBI for Kindle,” it’s out of date. Uploading a supported format avoids rejected files and conversion surprises, and sending advance readers a format their Kindle accepts saves everyone time. Amazon’s old KindleGen converter has also been retired; Kindle Previewer is the tool for checking how your file will look on Kindle devices.
Example
An author published her first novel in 2019 from a MOBI file. Now she wants to fix typos and add a link to her second book in the back matter. KDP won’t take a revised MOBI, so she exports a fresh EPUB from her manuscript, checks it in Kindle Previewer and uploads it to the existing title. The book keeps its ASIN and its reviews. For her advance readers, she sends the same EPUB, which they can load onto their Kindles through Send to Kindle.
Common mistakes
- Following outdated instructions that end with “convert to MOBI.”
- Sending MOBI files to advance readers. Send to Kindle won’t deliver them; EPUB works.
- Keeping MOBI as the only copy of a book. Keep the manuscript or an EPUB, so you can update the book when you need to.
- Assuming MOBI is what customers download. Amazon delivers its own formats, built from the file you upload.