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Archive format

XZ converter

An .xz file holds a single stream compressed with LZMA2, delivering some of the best ratios of any general-purpose compressor. It follows the Unix one-stream philosophy — pair it with tar as .tar.xz when multiple files need archiving.

Private for supported formats — processed in your browser

Convert supported files

Runs on your device

Drop XZ files here

Batch files can each use a different output. Nothing uploads for local conversions.

Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.

Where XZ comes from

The .xz container was released in 2009 by the XZ Utils project led by Lasse Collin, wrapping Igor Pavlov's LZMA2 algorithm in a robust, extensible format that superseded the interim .lzma files. Linux distributions, kernel.org, and GNU adopted it rapidly for release archives.

How XZ works

  • LZMA2 chunks the LZMA stream so state can reset, enabling multithreaded compression and better error recovery.
  • The container supports selectable integrity checks — CRC-32, CRC-64, or SHA-256 — plus filters such as BCJ branch conversion for executables.
  • Ratios typically land 25-30% better than gzip; compression is slow and memory-hungry while decompression is comparatively brisk.
  • An index block permits limited random access to compressed blocks, unusual among stream compressors.

When to use XZ

  • Software release tarballs where download size matters most.
  • Package internals — Debian .deb files carry data.tar.xz payloads.
  • Archiving large, rarely accessed datasets.
  • Compressed kernel and firmware images.

Strengths and limitations

Strengths

  • Elite compression ratios among widely deployed formats.
  • Strong, selectable integrity checking.
  • Standard tooling on every modern Unix.
  • Threaded compression via xz -T scales across cores.

Limitations

  • Slow and memory-intensive to compress; huge dictionaries can strain small devices even on decompression.
  • Single stream only — no file bundling without tar.
  • The 2024 XZ Utils backdoor incident (CVE-2024-3094) shook trust in the tool's supply chain, though the file format itself was never at fault.

Compatibility

Modern Linux distributions ship xz by default and macOS's bundled tar decompresses it via libarchive, with the standalone utility a package-manager install away. On Windows, 7-Zip and bsdtar both handle it, and libarchive compiled to WebAssembly enables browser-side extraction.

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