Archive Explorer

← All formats

AZW3 (KF8) file format

.azw3  ·  eBook (PalmDB variant)  ·  introduced 2011 by Amazon

What is a AZW3 (KF8) file?

AZW3, also known as KF8 (Kindle Format 8), is the eBook format Amazon introduced in 2011 to add HTML5 and CSS3 support over the older MOBI format. AZW3 typically wraps both KF8 and a fallback MOBI in the same file for compatibility with older Kindles.

Most readers reach this page after double-clicking a .azw3 file and finding their operating system unsure what to do with it. The good news: AZW3 (KF8) is a well-understood format with mature tooling on every major platform. It is supported in one click by mainstream archivers on Windows, macOS, and Linux.

How to extract a AZW3 (KF8) file

Opening a .azw3 file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

  1. Locate the .azw3 file in File Explorer.
  2. Right-click the file. If you have 7-Zip installed, choose 7-Zip → Extract Here. On Windows 11 the built-in extractor handles ZIP, 7z, RAR and several other formats directly through Extract All…
  3. If prompted, pick a destination folder and click Extract.
  4. The extracted files appear in a folder next to the original archive.

On macOS

  1. Find the .azw3 file in Finder.
  2. Install The Unarchiver from the Mac App Store, or Keka for both creating and extracting.
  3. Right-click the file → Open With → The Unarchiver (or just double-click after Unarchiver is set as the default).
  4. The extracted folder appears next to the archive.

On Linux

  1. Use your file manager: right-click the archive → Extract Here (file-roller on GNOME, Ark on KDE).
  2. On the command line, run one of: 
    7z x archive.azw3    # works for almost any format
  3. The files appear in the current directory.

How to create a AZW3 (KF8) file

To pack files into a .azw3 archive, you typically need an archiver that supports writing this format. Not every tool can create every format — for example, only WinRAR can create real RAR files. The sidebar lists the software known to read and write AZW3 (KF8).

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .azw3 files.

If you regularly create archives at scale, a dedicated archive automation suite can wrap this command in scheduled jobs, integrity checks, and offsite replication.

Strengths

  • HTML5/CSS3 layout
  • Embedded fonts

Weaknesses and limitations

  • Amazon-proprietary
  • DRM is common

Typical use cases

  • Modern Kindle eBooks (pre-KFX)
  • Self-published eBooks via KDP

Technical details

AZW3 (KF8) uses the PalmDB + HTML5 + CSS3 algorithm and is identified on disk by the magic byte sequence TPZ3. The standard MIME type is application/vnd.amazon.ebook. The format is a proprietary specification and is subject to license restrictions for some uses (notably creation).

Frequently asked questions

Is AZW3 (KF8) safe to open?

Archive files are containers — they are only as safe as what they contain. A .azw3 from a trusted source is fine; one received from a stranger can hold malicious executables, scripts, or files engineered to exploit bugs in your archiver. Always keep your archiver updated, and never run unknown executables that come out of an archive. A safe workflow is to extract into a sandbox and scan the contents before opening anything.

What is the maximum file size?

Modern implementations support archives in the multi-terabyte range. The practical limit is your filesystem (FAT32 caps at 4 GB; ext4, NTFS, APFS, and exFAT all comfortably handle multi-TB files).

Can I password-protect a AZW3 (KF8)?

Some archivers can wrap AZW3 (KF8) files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does AZW3 (KF8) compare to other formats?

See our format comparison pages such as ZIP vs 7z, ZIP vs RAR, and tar.gz vs tar.xz for side-by-side feature tables.

Related formats