What is a XZ file?

XZ — maximum compression

What is it?

XZ delivers the best compression ratio among the classic Unix formats, relying on the same algorithm as 7Z.

It is slow to compress but fast to decompress — a trade-off perfectly suited to software distribution: you compress once and decompress millions of times.

History & origin

XZ appeared in 2009 and quickly established itself as the standard format for distributing Linux source code, including the kernel itself.

It made headlines in 2024: a backdoor had been patiently inserted, over several years, into the tool that produces these archives. Discovered by chance, it targeted servers worldwide — one of the most sophisticated attack attempts ever observed in open-source software.

Why it is useful

The best compression ratio in the Unix world, paired with fast decompression.

An open, standardized format.

Limits & drawbacks

Compression is very slow and memory-intensive.

Like its relatives, it only handles a single file: TAR is still needed to archive a folder.

Practical tips

To share a .xz or .tar.xz file with someone on Windows, convert it to ZIP.

XZ works best for archiving large volumes of data that you'll decompress often but never recompress.

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