LZ File Converter (What lzip Archives Actually Are)

Where the .LZ Extension Actually Comes From

The .lz extension belongs to lzip, a compression format and command-line tool created by Antonio Diaz Diaz and first released in 2008. It's documented today in a published IETF Internet-Draft that also formally registers "application/lzip" as a media type, which is a more thorough level of specification than many older Unix compression formats ever received. Lzip compresses data using LZMA — the same core algorithm that powers 7-Zip's default 7z format and the xz format — but wraps that compressed data in a container designed around one explicit priority: making it easy to detect exactly what went wrong if a file gets corrupted.

Every lzip file begins with a fixed four-byte signature: 0x4C 0x5A 0x49 0x50, which spells out "LZIP" in ASCII. Right after that comes a version byte and a single coded byte describing the dictionary size the compressor used, then the LZMA-compressed data itself, and finally a trailer holding three separate values — a CRC32 of the original uncompressed data, that data's exact size in bytes, and the size of the compressed member. Lzip's own documentation describes this trailer as a "3-factor integrity check," a specific design choice meant to catch corruption that a single whole-file checksum might miss.

Why Lzip's Own Documentation Argues Against a Format Like XZ

Lzip's project documentation includes a specific page titled "Xz format inadequate for long-term archiving," which lays out named, technical objections to the xz container rather than vague preference. It states that none of xz's many internal length fields are protected by a checksum, that xz's variable-length integer encoding can suffer what the page calls a "double framing error" — where a single corrupted byte changes both a field's value and how many bytes make up that field — and that xz's own integrity check is optional per stream rather than mandatory. Lzip's documentation contrasts this directly against its own design, stating that lzip protects all of its length fields and requires no optional check types to begin with, positioning it as the more conservative choice specifically for archives meant to remain verifiably intact decades from now.

That focus on integrity over raw speed or convenience is why lzip ships with a companion recovery utility, lziprecover, built specifically to use the format's own three-factor trailer to recover as much data as possible from a damaged .lz file. Lzip compresses only a single continuous data stream at a time — there's no built-in concept of multiple files the way ZIP has — so archiving more than one file as .lz means running tar first, producing the combined ".tar.lz" extension that GNU Automake documents directly through its own "dist-lzip" option.

The dictionary-size byte lzip encodes right after its version byte is worth understanding on its own: rather than storing a raw dictionary size directly, lzip codes it compactly, and the format has changed exactly how that byte gets interpreted across its own version history, which is why lzip's own release notes document specific compatibility notes between older and newer builds decompressing files from the other. In practice, this rarely causes trouble, since lzip has stayed a small, slow-moving project with relatively few released versions compared with something like gzip or xz.

What You Gain and Lose by Converting an LZ Archive

• Lose — lzip's three-factor integrity check: the separate CRC32, data-size, and member-size verification recorded in lzip's own trailer has no exact equivalent in most other common archive formats.
• Gain — far broader native software support: most current archive tools handle formats like ZIP or 7z directly, while lzip generally needs a dedicated package or a specific plugin installed first, especially on Windows.
• Lose — access to lzip's own recovery tooling: lziprecover is built specifically around lzip's trailer format to repair damaged .lz files, a capability tied to that exact container.
• Gain — faster compression in many cases: lzip's LZMA-based compression is markedly slower than gzip's DEFLATE at comparable settings, so moving to a faster-compressing format can matter for large, frequently rebuilt archives.
• Lose — nothing about the actual decompressed file contents: extracting an .lz file and repacking the same data into another format changes only the container and checksums, not the underlying bytes once decompressed.

Which Current Programs Can Actually Open an .LZ File

GNU tar has supported lzip transparently since version 1.23, through its own --lzip option, letting a .tar.lz archive be extracted the same way any other compressed tarball would be. GNOME's Archive Manager opens the format directly on Linux desktops, and real, documented adopters include the IANA Time Zone Database, which ships some releases as .lz files, and the Linux-libre kernel project, which distributes some files this way too.

Windows and macOS tell a much narrower story. 7-Zip does not include native lzip support in its standard build; opening or creating .lz files with it requires a separate add-on called the Lzip7z plugin, distributed independently of the main 7-Zip project. WinRAR's own documented list of formats it can open — covering RAR, ZIP, and extraction support for 7z, ISO, JAR, BZ2, GZ, TAR, ARJ, and several others — does not include lzip at all. Bandizip, a Windows archive manager, is one of the few mainstream tools whose own documentation lists direct lzip support without needing a separate plugin first.

macOS's built-in Archive Utility has no documented native lzip support either, which puts it in roughly the same position as stock 7-Zip on Windows — a specific third-party tool or a package manager like Homebrew, which distributes lzip itself as an installable command-line package, is generally needed before an .lz file opens on a Mac at all. This narrow support picture is precisely why so many .lz downloads that originate from Linux-centric or GNU-affiliated projects come as a surprise to Windows and Mac users who assumed their existing archive tool would simply handle it.

The Specific Problems People Actually Run Into With LZ Files

A documented, recurring pattern on 7-Zip's own SourceForge discussion forums involves people downloading a .tar.lz or plain .lz release from a GNU or Linux project and discovering that stock 7-Zip simply doesn't recognize the extension. The usual paths from there are installing the separate Lzip7z plugin or asking whoever published the file for a more common alternative like .tar.gz — this isn't a broken download, it's a genuine support gap between what the project chose to publish and what a typical Windows toolchain already understands.

A second real issue traces back to compression speed itself: because lzip uses LZMA rather than DEFLATE, compressing large files takes noticeably longer than gzip at comparable settings, according to lzip's own published benchmark data — something people building a large .lz archive for the first time sometimes don't expect, mistaking a long wait for a stalled or frozen process.

A third pattern involves mixed-OS teams specifically: a Linux-based build server defaults to producing .lz release artifacts because its toolchain already includes lzip, while Windows-based teammates without the Lzip7z plugin installed simply can't open the files at all. That's a documented compatibility gap rather than file corruption, and the practical fix is either installing the plugin or having the build server also emit a more broadly supported format alongside it.

LZ/lzip Facts Worth Knowing at a Glance

Common Questions About Opening and Converting LZ Files

What's the difference between .lz and .tar.lz?
A plain .lz file is lzip-compressed data from a single stream. A .tar.lz file is a tar archive of multiple files that has then been compressed with lzip — the same two-step pattern .tar.gz uses with gzip instead.

Why won't 7-Zip open my .lz file?
Because the standard 7-Zip release doesn't include native lzip support. The separate Lzip7z plugin, or a tool like Bandizip that documents lzip support directly, needs to be installed first.

Is lzip the same thing as LZMA or xz?
No. Lzip uses LZMA as its compression algorithm, the same core method xz and 7z also use, but each wraps that compressed data in its own separate container format with its own integrity-checking design.

Why do some projects choose lzip instead of the more common gzip or xz?
Mainly for its documented 3-factor integrity check and specific, published objections to xz's container design, both aimed at long-term archival reliability rather than speed or the widest possible software support.

What happens if my .lz file gets corrupted?
Lzip ships with a dedicated tool, lziprecover, built specifically to use the format's own CRC32, data-size, and member-size trailer to recover as much of the original data as possible.

Does GNU tar support lzip archives directly?
Yes, since version 1.23, through its own --lzip option, which lets a .tar.lz archive be extracted the same way any other compressed tarball would be, without a separate lzip installation step.