Amazon Kindle has the largest eBooks capacity in the world, and (maybe) the most complicated eBooks format mechanism. In the most of other eBook stores, we usually get only two formats: EPUB and PDF. While in Amazon Kindle, we can see AZW, AZW3, PRC, Mobi, HTMLZ, and more...
Although a Kindle book can be delivered as any of these formats and almost looks the same. In fact there is difference between them, it might be tiny, but you shall not ignore it.
Following are detailed introduction and explaination.
What is AZW
AZW is the most popular format for Amazon Kindle books, it might stand for Amazon Word, but Amazon hasn't officially confirm that yet.
If we sync the purchased Kindle books to local computer via Kindle for PC/Mac, the synced books are usually saved in .azw format and protected by Kindle DRM.
If an AZW file's DRM protection is eliminated, it can be directly renamed to Mobi while keeping the file complete and read by the reader software like Kindle for PC or MobiPocket Reader.
To remove DRM from AZW is pretty simple, just make sure the files are synced via Kindle for PC/Mac, then use Kindle DRM Removal to handle them, no extra job is required.
Here is a brief guide: Remove DRM from Amazon Kindle AZW files
What is AZW3 (KF8)
AZW3 is a variation of AZW and also known as KF8. At the beginning it was only supported by Kindle Fire tablet, and later expanded to forth generation of Kindle, and Kindle for PC/Mac.
Compared to AZW or Mobi, it is more advanced by supporting more styles, fonts and layout. And I can see the trends that AZW3 is gradually replacing Mobi.
At the moment, books directly downloaded to recent generations E-Ink Kindle are uaually delivered as AZW3 format and protected by DRM. While some AZW files synced by Kindle for PC/Mac would also turn to AZW3 after the DRM protection is removed.
If you want to strip the DRM from AZW3 files downloaded on E-Ink Kindle, please read: How to Remove DRM From AZW3 eBook Files
PRC and Mobi
When a PRC file and a Mobi file are all DRM-free, then we can simply say they are exactly the same thing. But when they are protected by DRM, things are going differently.
If a purchased Kindle book is downloaded to Android device, in other words, synced by Kindle for Android app, then the format would be PRC. And we shall note that Kindle Fire tablets are also Android devices in actual, so the books directly downloaded to Kindle Fire tablets would also save as PRC format.
Read this post you can know how to remove Kindle DRM with Android devices: PRC DRM Removal for Kindle Android Books
And the most of Mobi books are DRM-free nowadays, as Amazon transform them to AZW once they are protected by DRM.
Topaz (TPZ, or AZW1)
Generally speaking, all the formats above are basically generated upon Mobi and AZW, but the Topaz, or the variations TPZ and AZW1, are pretty different. And the difference mainly manifest in the file structure and data base, that's not what we are discussing here.
The Topaz files are always DRM-free, when thy are protected by Kindle, they change to TPZ or AZW1.
If a Topaz book synced via Kindle's Whispersync, it becomes AZW1; if directly downloaded from the website, it becomes TPZ.
Remove DRM from TPZ/AZW1 books are the same as from AZW, so you can also read this guide: Remove DRM from Amazon Kindle TPZ, AZW1, Topaz files
And the HTMLZ? It is just a zip archive of HTML files.
AZW6 files are very rare, they mainly appear in Japan Kindle store's manga books.
AZW6 file only contains texts, all the images in the book are saved in the related folder. So if you convert an AZW6 book to another format, all the images will be gone, as they are not contained in the book.
But why? All AZW6 books I got contain lots of images, Amazon make it work like this for better reading experience.
Imagine you buy a Kindke AZW6 book (you don't know its format before buying) in a place with poor WiFi network, then this book will download low quality images, you needn't wait a long time to start reading the book. When you go to a place with strong WiFi, Kindle will download high quality images to replace those low quality images automatically.
KFX is the latest format of Amazon Kindle, to get this format of file you must have an E-Ink Kindle, and the book should have the "Enhanced Typesettings" property (you can find this property in Amazon product page).
KFX is the successor of AZW6, it's even not a real eBook file. You can see it as a downloader, it downloads all the stuff of a book into your Kindle, no matter texts or images.
So there is no change at all to convert a KFX file to another format or decrypt a KFX file.
However, you have alternative solution to convert KFX to Mobi/EPUB/PDF.
Infographic about these defferences
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Jonny Greenwood joined Epubor since 2011, loves everything about eBooks and eReaders. He seeks the methods to read eBooks more freely and wants to share all he has got with you.