The LZMA SDK is a software development kit from the 7-Zip project. It provides documentation, samples, header files, libraries and tools for building applications that use LZMA compression.[1] Unlike 7-Zip itself, which is mainly under the GNU LGPL,[4] the LZMA SDK is in the public domain. Anyone may copy, modify, publish, use, compile, sell or distribute the original LZMA SDK code, in source or binary form, for any purpose, commercial or non-commercial (rule).[1] The 7-Zip FAQ describes the SDK as available “under a more liberal license” than 7-Zip.[9] This article also covers 7-Zip Extra and the third-party code bundled in 7z.dll.
Editions
| Package | Contents (vendor wording) | Licence |
|---|---|---|
| LZMA SDK | C++ LZMA encoder and decoder; C++ .7z compression and decompression (reduced version); ANSI-C LZMA / LZMA2 / XZ code; ANSI-C 7z decompression; C# and Java LZMA code; lzma.exe; 7zr.exe; SFX modules[1] | Public domain[1] |
| 7-Zip Extra | Standalone console version, 7z DLL, Plugin for Far Manager[6] | GNU LGPL; 7z.dll also BSD and unRAR terms[4] |
| 7zr.exe | 7-Zip console executable (x86)[6] | Also shipped in the LZMA SDK as a reduced version of 7z.exe[1] |
The ANSI-C and C++ source code in the LZMA SDK is a subset of the 7-Zip source code.[1] The 7z format code is part of 7-Zip, which is distributed under the GNU LGPL, and most of it is also included in the LZMA SDK.[7] As commentary: the same algorithm can therefore reach a product under two different licences. The licence depends on which package the code was taken from. SAM and open-source review records should note whether a component came from the LZMA SDK or from the 7-Zip source tree.
LZMA SDK licence and versions
The SDK version history says the SDK was placed in the public domain in version 4.62.[1] The current version is 26.03, dated 2026-09-03. Its release note says bugs and vulnerabilities were fixed.[1] SPDX lists the SDK licence as “LZMA SDK License (versions 9.22 and beyond)”, with identifier LZMA-SDK-9.22. A separate identifier covers versions 9.11 to 9.20.[2][3] SPDX notes that the licence text on the 7-Zip SDK web page does not match the texts in any of the SDK distributions.[2] The SPDX list marks LZMA-SDK-9.22 as neither FSF Free/Libre nor OSI Approved.[3] As commentary, this reflects SPDX’s own review status. It is not a finding that the terms are restrictive.
The LZMA SDK has no notice, attribution or source-availability condition, because the web page places it in the public domain for any purpose.[1] Inside the 7-Zip source tree, some files are also public domain where the file itself says so. Files with no licence information default to the GNU LGPL.[5]
Third-party code in 7z.dll
7z.dll is the 7-Zip component that carries more than one licence.[4]
| Code | Origin | Licence | Catalog rule |
|---|---|---|---|
| RAR decompression | Developed using unRAR source code; copyright Alexander Roshal | GNU LGPL with unRAR licence restriction | unRAR restriction |
| LZFSE decompression | Derived from the LZFSE compression library by Apple Inc. | BSD 3-clause | BSD 3-clause components |
| ZSTD decompression | Developed using the zstd decoder by Facebook, Inc. as reference code | BSD 3-clause | BSD 3-clause components |
| XXH64 hash | Derived from original XXH64 code by Yann Collet | BSD 2-clause | XXH64 |
Source: 7-Zip licence file.[4] The source tree names the files: CPP/7zip/Compress/Rar* files, CPP/7zip/Compress/LzfseDecoder.cpp, C/ZstdDec.c and C/Xxh64.c (rule).[5] Copies of 7z.dll distributed on their own, for example from 7-Zip Extra, carry the same licence mix. The licence file requires binary redistributions to reproduce the related licence information.[4][6]
Related programs by the same author
7-Zip’s website links to 7-max, a separate program that runs applications with large (2 MB) memory pages. 7-max is distributed as free software under the GNU LGPL. Its page warns that it can be unstable on some systems.[8] It is not part of the 7-Zip distribution.
Out of scope
This page does not cover third-party LZMA ports and bindings that the SDK page links to, whose licences are set by their own authors. It also does not cover XZ Utils, or the licensing of RAR and WinRAR.[1]