zstd

Updated

September 4, 2026

Overview

zstd (Zstandard) is a modern compression tool offering an excellent speed vs ratio curve, levels from very fast to extremely dense, optional multithreading, and framing with checksums. It is the preferred default for many new local pipelines, package systems, and container layers. Extension: .zst.

Syntax

zstd [options] [file...]
zstd -d [options] [file...]
zstdcat [file...]
unzstd [file...]

Common Options

Option Description
-d, --decompress Decompress
-c, --stdout Write to stdout
-f, --force Overwrite / compress links
-o file Output file name
-k / --rm Keep sources (default keep) / remove sources after success
-t Test integrity
-T# Threads (-T0 = all cores)
-# Level 1–19 (default 3); ultra with --ultra -20…-22
-v Verbose
-q Quiet
-l / --list Show frame info
--train Build a dictionary (advanced)
-D dict Compress/decompress with dictionary
--long Long distance matching mode

Unlike classic gzip defaults, zstd keeps the original file unless you pass --rm.

Examples with Explanations

Basic

zstd file.tar
zstd -d file.tar.zst
zstd -o out.zst file
unzstd file.tar.zst

Levels and threads

zstd -1 -T0 fast.log
zstd -19 -T0 cold.img
zstd --ultra -22 -T0 deepest.img   # very slow/heavy
for l in 1 3 6 9 15 19; do
  zstd -$l -f -o /tmp/t.zst sample.bin && ls -lh /tmp/t.zst
done

Pipelines with tar

tar -I 'zstd -T0' -cf backup.tar.zst dir/
tar --zstd -cf backup.tar.zst dir/          # GNU tar 1.31+
zstd -dc backup.tar.zst | tar xf -
tar -I zstd -xf backup.tar.zst

Integrity

zstd -t backup.tar.zst
zstd -l backup.tar.zst

Remove source when desired

zstd --rm big.img

Dictionaries (small similar files)

zstd --train -o dict samples/*
zstd -D dict small1 small2
zstd -d -D dict small1.zst

Useful for massive numbers of similar tiny JSON/logs.

Notes / Pitfalls

  • Confirm consumers understand .zst before replacing gzip in public APIs.
  • Ultra levels need large memory windows — watch small VMs.
  • Default keeps inputs; scripts ported from gzip may leave duplicates if they assume deletion.
  • tar --zstd requires sufficiently new GNU tar; -I 'zstd -T0' is explicit and flexible.
  • Older enterprise appliances may still demand .gz.

2026-relevant notes

  • Default choice for many new internal artifacts, caches, and log archives.
  • Kernel squashfs, package managers, and container tooling increasingly support zstd natively.
  • Compare: gzip (universal), xz (max ratio, slow), zstd (best general default).

Additional Resources