I've a book in the .azw3 extension. There are two files included with it in the same folder which are cover.jpg and metadata.opf.

Should I keep these files?

Note: I use Kindle Previewer or Calibre for Microsoft Windows to open the .azw3 file.

  • @DavidPostill This is being used on my computer, I use Calibre or Kindle Previewer to open it! I don't have the kindle device by the way!
    – Omar
    Feb 7, 2015 at 11:32
  • Close vote retracted. Please edit your question to include this extra information (operating system and software used).
    – DavidPostill
    Feb 7, 2015 at 11:33
  • Calibre generates the opf file & uses the jpg itself to display the cover. They're not important to transfer to a reader, but are useful on the desktop machine. Note: Calibre doesn't like its file structure being edited from Explorer.
    – Tetsujin
    Feb 7, 2015 at 11:48
  • @Tetsujin Would deleting these files cause any information loss? If I want to give the book to a friend should I give him the .azw3 file only, or the 3 files in order not to make any information loss?
    – Omar
    Feb 7, 2015 at 12:57
  • possible information-loss, for instance if the book was already converted from one format to another, then without the opf further translating it to a 3rd format would lose the 'other info' that Calibre has neatly tucked away in that file. Just to read the book as is on another device would cause no real issues. I'm not certain whether azw3 keeps the book cover in its own format - if it does no worries, if it doesn't, it will be missing the cover for the next reader. Overall, nothing hugely disastrous will happen without the extra files.
    – Tetsujin
    Feb 7, 2015 at 13:48

1 Answer 1


Both the cover.jpg and metadata.opf files are generated by Calibre to preview the cover and metadata of the book. Calibre generates those files from embedded information in the .azw3 file.

So the two files are useless if you're giving the book to a friend or saving it in a separate folder from the one Calibre uses to read the book. However, be cautious not to delete the two files generated in the folder Calibre is using.

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