What is XZ?

XZ is a general-purpose data compression format using the LZMA2 (Lempel-Ziv-Markov chain Algorithm 2) compression algorithm. It typically achieves 15-30% better compression than gzip and 5-10% better than bzip2, making it ideal for distributing large files. XZ supports integrity checking (CRC64/SHA-256), block-based compression for parallel processing, and flexible compression levels.

XZ is the standard compression format for Linux kernel releases, software packages (.tar.xz), and many open-source projects. Popular Linux distributions use XZ for package managers (Arch Linux, Fedora) and system backups. The format is designed as a modern replacement for gzip and bzip2, offering superior compression at the cost of slower compression speed (but fast decompression).

Did you know? The Linux kernel switched from bzip2 to XZ in 2013 for better compression!

History

XZ was created to provide a modern, efficient compression format with better ratios than existing tools while remaining free and open-source.

Key Milestones

  • 2005: LZMA algorithm developed
  • 2009: XZ format specification released
  • 2011: Linux distributions adopt XZ
  • 2013: Linux kernel uses XZ
  • 2015: Wide adoption in open-source
  • Present: Standard Linux compression format

Key Features

Core Capabilities

  • LZMA2 Algorithm: Excellent compression ratio
  • Integrity Checks: CRC64, SHA-256
  • Block Compression: Parallel processing
  • Multiple Filters: Optimized for data types
  • Fast Decompression: Efficient extraction
  • Open Standard: Public domain format

Common Use Cases

Linux Packages

Software distribution

Archives

File compression (.tar.xz)

Source Code

Open-source releases

Backups

System backup compression

Advantages

  • Best compression ratio
  • Fast decompression
  • Built-in integrity checking
  • Standard on Linux systems
  • Open and free format
  • Block-based for parallel processing
  • Better than gzip/bzip2

Disadvantages

  • Slow compression speed
  • High memory usage during compression
  • Limited Windows native support
  • Not as universal as ZIP/GZIP
  • Compression time vs ratio tradeoff

Technical Information

Format Specifications

Specification Details
File Extension .xz, .txz (tar.xz)
MIME Type application/x-xz
Algorithm LZMA2
Compression Levels 0-9 (higher = better compression)
Checksums CRC32, CRC64, SHA-256
Typical Ratio 15-30% better than gzip

Common Tools

  • Command Line: xz, unxz, xzcat (Linux/macOS)
  • Archivers: 7-Zip, PeaZip, WinRAR
  • Package Managers: tar (with -J flag), pacman
  • Libraries: liblzma, XZ Utils