Amazon has largely moved to the AZW3 (Kindle Format 8) for newer books.
MOBI (short for Mobipocket) is a reflowable ebook format. Unlike PDFs, which have a fixed layout, MOBI text adjusts automatically to fit the screen size and orientation of your device.
Tools like the "MOBI Reader" extension for Chrome allow you to read ebooks directly in your browser. MOBI Support for eBooks Frequently Asked Questions
You don't need a Kindle hardware device to read these files. You can use:
Websites like Project Gutenberg offer thousands of public domain books in MOBI format for free download.
You can use Amazon’s Send to Kindle service to wirelessly deliver MOBI files from your computer to your Kindle account. 4. Opening MOBI Files on Other Devices
As of early 2025, Amazon no longer accepts MOBI for new ebook submissions on Kindle Direct Publishing (KDP), preferring EPUB or KPF instead. 2. How to Create or Convert MOBI Files
If you have a manuscript or a document in another format (like PDF or Word), you can easily turn it into a MOBI file using various tools: