What is the AZW file format?
.azw is an ebook format associated with Amazon Kindle, introduced in November 2007 with the first-generation Kindle device. It is based on the Mobipocket .prc standard, using a Palm Database (PDB) container. .azw ebooks can be purchased and downloaded directly to the device, or transferred from a computer via USB.
Most .azw files employ Amazon's DRM copyright protection system, locking each book to a specific Amazon account. DRM-protected .azw files may only be opened on authorized Kindle devices or compatible apps. Non-protected .azw files are in fact structurally equivalent to .prc files and can be freely converted - for example, in Calibre.
Amazon later superseded .azw with .azw3 (Kindle Format 8, 2011) and .kfx (2015), which support richer content. Older .azw titles remain compatible with current Kindle apps and hardware.
Security & safety
RISK: LOWAZW is e-book data and safe to read. The real friction is DRM, not malware: books bought from Amazon are account-locked, so generic apps refuse them and conversion is blocked - a rights restriction, not a virus. Removing DRM violates Amazon's terms and may be unlawful where you live. The practical risk is pirated-e-book download sites (bundled adware/fake downloads). Treat DRM-free AZW files as ordinary documents.
Format details
in a nutshellFULL NAMEAmazon Kindle eBook (AZW)aka Kindle File Format, AZW1
DEVELOPERAmazon.com, Inc.since 2007 (with the first Amazon Kindle)
CATEGORYeBook Files
MIME TYPEapplication/vnd.amazon.ebook
TYPEAmazon Kindle e-book (Palm Database/PDB-based MOBI container) with Amazon DRM
This extension is also used by…
- AZW1 / Topaz Kindle book - Older Amazon Topaz e-book format using the same .azw1 family; structurally different ('TPZ' header) and rarely seen today.
MAGIC BYTES · FILE SIGNATURE
OFFSET
3c3d3e3f40414243
HEX
424F4F4B4D4F4249
ASCII
BOOKMOBI
AZW is a Palm Database (PDB) file like MOBI. There is no fixed magic at offset 0 (first 60 bytes are the variable book name). At offset 60 sit the 8 ASCII bytes "BOOKMOBI" (42 4F 4F 4B 4D 4F 42 49) = type "BOOK" + creator "MOBI". An AZW is essentially a MOBI wrapped with Amazon DRM. The unrelated older AZW1/Topaz variant instead begins with "TPZ" and is a different internal structure.
Programs that open AZW files
Windows2 apps
Calibre
Open-source Add a DRM-free .azw to the library to read in the viewer and convert it (EPUB/PDF). DRM books won't import without authorisation. 
Kindle for PC
Free Read AZW books delivered to your Amazon account; the official reader for DRM-protected purchases. 
macOS2 apps
Linux2 apps
Calibre
Open-source Primary option on Linux: add the .azw, read in the built-in viewer, convert to EPUB/PDF (DRM-free files). 
Android3 apps
Amazon Kindle (app)
Free Read Kindle books on your account; sideload a DRM-free AZW via the app's import or Documents folder.
iOS1 app
Technical details
deep spec| Container format | Palm Database (PDB) - type "BOOK", creator "MOBI" |
| Magic identifier | `BOOKMOBI` (hex `42 4F 4F 4B 4D 4F 42 49`) at byte offset 60 |
| Byte order | Big-endian |
| Text compression | PalmDOC (LZ77-based); HUFF/CDIC used for larger records |
| Text content model | PalmDOC-compressed HTML subset stored across multiple PDB records |
| MOBI header version | Version 6 (AZW); Kindle Format 8 / AZW3 uses version 8 |
| DRM implementation | Amazon account-locked voucher; DRM-free variant is structurally identical to `.mobi` |
| MIME type | `application/vnd.amazon.ebook` |
| Metadata block | EXTH header carries ASIN, CDE type/key, author, publisher, and cover offset |
| Image storage | Embedded as separate PDB records (JPEG or GIF); no PNG support in original AZW |
| Typical file size | 300 KB - 25 MB (plain-text titles small; image-heavy or fixed-layout titles larger) |
| Successor formats | `.azw3` (Kindle Format 8, 2011) adds CSS3/HTML5; `.kfx` (2015) for current Kindle hardware |
| Released | 2007 (with the first Amazon Kindle) |
| Latest version | AZW (original Kindle format); superseded by AZW3/KF8 (2011) and KFX (2015) |
| Specification | wiki.mobileread.com |
AZW conversions
Possible
.AZW .PRCOnline converter
How to convert
.AZW .PDFOnline converter
Yes, AZW converts to PDF -- the fastest way is Calibre: add the file, right-click, Convert books > Convert…
How to convert
.AZW .MOBIOnline converter
Yes - Calibre converts a DRM-free AZW to MOBI in a few clicks, but books bought from the Kindle Store are…
How to convert
.AZW .EPUBOnline converter
Yes, AZW converts to EPUB in Calibre - but only if the file has no DRM.
How to convert
.AZW .TXTOnline converter
Yes -- Calibre converts any DRM-free AZW (Amazon Kindle e-book) file to plain text on Windows, macOS, and…
How to convert
.AZW .RTFOnline converter
Yes, AZW converts to RTF -- use Calibre: add the file, right-click, Convert books > Convert individually, set…
How to convert
.AZW .AZW3Online converter
Yes, AZW converts to AZW3 -- use Calibre: add the file, right-click, Convert books > Convert individually,…
How to convert
.AZW .DOCXOnline converter
Yes, you can convert AZW to DOCX with Calibre, as long as the file has no DRM.
How to convert
Not possible
Community Q&A
asked by usersNo questions yet - be the first to ask about AZW files.
Frequently asked questions
How do I open an AZW file?
Read it on a Kindle device or the free Kindle app (for account books), or open a DRM-free AZW in Calibre on Windows/macOS/Linux. Calibre also converts DRM-free AZW to EPUB or PDF. DRM-protected purchases only open in official Kindle apps.
How do I convert AZW to EPUB?
Use Calibre: add the file, click Convert, choose EPUB. This works on DRM-free AZW. Books bought from Amazon are DRM-protected and can't be converted without removing the protection (against Amazon's terms).
What's the difference between AZW, AZW3 and MOBI?
All share the Palm-DB lineage. MOBI is the original Mobipocket format; AZW is MOBI plus early Kindle DRM (2007); AZW3 (KF8, 2011) is the newer, better-styled Kindle format. KFX (2015) is the current one.
Why won't my AZW file open or convert?
Almost always DRM: AZW books bought from Amazon are account-locked, so Calibre and generic readers refuse them. DRM-free AZW files (your own, or free books) open and convert without issue.
How do I read an AZW on my phone?
Use the Amazon Kindle app (account books, plus sideloaded DRM-free files), or a reader like Moon+ Reader or Cool Reader for DRM-free AZW/MOBI in device storage.
Is it legal to convert AZW to PDF?
Converting your own DRM-free books is fine. Stripping DRM from purchased Kindle books to convert them breaks Amazon's terms and may be unlawful where you live, even for personal use.
References
1MobileRead Wiki - AZW formatwiki.mobileread.com
2Amazon - Send to Kindle (supported file types)www.amazon.com
