Amazon's Kindle reader devices support ebooks in several formats. Books purchased at the Kindle Store are in Amazon's AZW format. The Kindle also supports PDF files, plain text files, Mobipocket files ending in MOBI and PRC, Audible files ending in AA and AAX and MP3 files. Only unprotected or non-DRM MOBI files are supported on the Kindle. If you purchased the MOBI book it may have protection that will prevent you from reading it on the Kindle. Files converted to the MOBI format or downloaded for free are usually unprotected.
Plug the Kindle into your computer using the USB cable that came with the Kindle and turn it on. The Kindle enters USB Drive Mode and is unavailable for reading during this period.
Click the "Computer" shortcut in the "Start" menu. On Mac systems, open a new Finder window. Double-click the "Kindle" drive to open it as you would any other external drive.
Open the "documents" folder in the Kindle drive. Open a new Windows Explorer window or Finder window and navigate to the location of your MOBI file.
Click and drag the MOBI file to the Kindle "documents" folder to copy it to the Kindle. Eject the Kindle drive from your computer. The MOBI ebook file is accessible from the main menu of the Kindle just like books purchased at the Kindle Store.
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