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LZ4 file format

.lz4  ·  compression (single file)  ·  introduced 2011 by Yann Collet

What is a LZ4 file?

LZ4 is an extremely fast compression algorithm focused on speed rather than ratio. It can compress at gigabytes per second and decompress even faster, making it the choice when CPU is the bottleneck. ZFS, the Linux kernel boot image, and many databases use LZ4 internally.

Most readers reach this page after double-clicking a .lz4 file and finding their operating system unsure what to do with it. The good news: LZ4 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 LZ4 file

Opening a .lz4 file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

  1. Locate the .lz4 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 .lz4 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.lz4    # works for almost any format
  3. The files appear in the current directory.

How to create a LZ4 file

To pack files into a .lz4 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 LZ4.

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .lz4 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

  • Blazing fast compression and decompression
  • Low CPU overhead
  • Open and stable format

Weaknesses and limitations

  • Modest compression ratio
  • Single file only

Typical use cases

  • ZFS/Btrfs transparent compression
  • Linux kernel boot images
  • In-memory databases
  • Real-time game asset streaming

Technical details

LZ4 uses the LZ77 family (LZ4) algorithm and is identified on disk by the magic byte sequence 04 22 4D 18. The standard MIME type is application/x-lz4. The format is an open specification and is free for any use.

Frequently asked questions

Is LZ4 safe to open?

Archive files are containers — they are only as safe as what they contain. A .lz4 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 LZ4?

Some archivers can wrap LZ4 files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does LZ4 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.

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