What is the TZ file format?
The .tz extension marks a TAR archive compressed with the Unix compress utility using the LZW (Lempel-Ziv-Welch) algorithm. It is a shorthand alias for .tar.Z and is interchangeable with .taz - all three names describe the same binary structure.
Internally, a .tz file consists of an outer .Z compress envelope - identifiable by the two-byte magic 1F 9D at the start of the file - wrapping a standard TAR archive. The TAR layer contains 512-byte header blocks for each member file followed by padded data, while the LZW layer compresses the entire TAR stream using up to 16-bit codes. GNU tar handles both layers transparently using its -Z flag: tar -xZf archive.tz.
The format dates to the early 1980s when Unix compress was the dominant compression tool. It was widely used to distribute Unix software and academic data throughout the late 1980s and early 1990s, particularly when floppy disks were the primary exchange medium. .tz archives are found today mainly in legacy Unix repositories and old backup sets.
Modern equivalents - .tar.gz (gzip, 1992), .tar.bz2 (bzip2, 1996), .tar.xz (xz, 2009), and .tar.zst (Zstandard, 2016) - all offer better compression ratios and have supplanted .tz for new archives. Tools such as 7-Zip, PeaZip, and WinZip can extract .tz files on Windows.
Security & safety
RISK: LOW.tz is a passive archive container; the .Z format has no executable capability. Standard archive safety cautions apply: a crafted tarball can contain path-traversal entries ('../', absolute paths - the "tar slip" attack). Extract untrusted .tz files into an empty directory and review contents before running anything inside.
Format details
in a nutshell- Timezone data (tz database) - Historically some IANA tz (timezone) database distributions were packaged as .tz or tzdata.tar.gz; not a distinct file format.
Programs that open TZ files
Windows4 apps
WinZip
Paid Open the .tz and Extract; WinZip handles .Z compressed archives. 7-Zip is a free alternative. 
7-Zip
Open-source Right-click the .tz → 7-Zip → Extract Here. 7-Zip decompresses the .Z layer and extracts the tar in one step. 
macOS3 apps
The Unarchiver
Free Double-click the .tz to extract via The Unarchiver (may handle .Z-compressed archives). 
StuffIt Deluxe
Paid Historically supported .Z and .tar.Z extraction on macOS. Smith Micro Software still sells StuffIt, but verify current macOS version compatibility. 
tar / zcat (built-in Terminal)
Built-in Run: zcat file.tz | tar -xf - or tar -xZf file.tz (macOS bsdtar supports -Z). No extra install needed. 
Linux2 apps
gunzip
Open-source gunzip cannot decompress .Z (LZW compress) files - use zcat/uncompress or tar -xZf instead. Listing gunzip here is INCORRECT (see db_audit_notes).
tar (GNU tar, CLI)
Open-source tar -xZf file.tz extracts the archive. GNU tar's -Z flag invokes uncompress/compress transparently. Also: zcat file.tz | tar -xf -. Technical details
deep spec| Container structure | TAR archive wrapped in a Unix compress (.Z) LZW envelope |
| Magic bytes (outer .Z) | 1F 9D at offset 0 |
| Compression algorithm | LZW (Lempel-Ziv-Welch) via Unix compress; up to 16-bit codes by default |
| Inner archive format | Standard TAR: 512-byte header blocks + padded file data per member |
| Byte order | N/A - LZW bitstream; TAR headers use ASCII fields |
| Encoding | Binary |
| Checksum | TAR per-member header octal checksum only; no outer-layer checksum |
| Equivalent names | `.tar.Z` and `.taz` are identical formats |
| GNU tar flag | `-Z` enables transparent compress/decompress (e.g. `tar -xZf file.tz`) |
| Typical file size | Tens of KB to hundreds of MB |
| MIME type | application/x-tar (also application/x-compress) |
| LZW patent status | Unisys patent expired 2003; IBM patent expired 2004 - no longer encumbered |
| Superseded by | `.tar.gz`, `.tar.bz2`, `.tar.xz`, and `.tar.zst` (better compression ratios and speed) |
| Released | early 1980s (Unix compress tool, 1984; .tz/.taz shorthand in common use by late 1980s) |
| Latest version | N/A (format is static; no versioning) |
| Open standard | Yes · royalty-free |
| Specification | www.gnu.org |
TZ conversions
Community Q&A
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