7-Zip is a free and open-sourcefile archiver, a utility used to place groups of files within compressed containers known as "archives". It is developed by Igor Pavlov and was first released in 1999.[2] 7-Zip has its own archive format called 7z, but can read and write several others.
By default, 7-Zip creates 7z-format archives with a .7zfile extension. Each archive can contain multiple directories and files. As a container format, security or size reduction are achieved by looking for similarities throughout the data using a stacked combination of filters. These can consist of pre-processors, compression algorithms, and encryption filters.
The core 7z compression uses a variety of algorithms, the most common of which are bzip2, PPMd, LZMA2, and LZMA. Developed by Pavlov, LZMA is a relatively new system, making its debut as part of the 7z format. LZMA uses an LZ-based sliding dictionary of up to 3840 MB in size, backed by a range coder.[15]
In 2011, TopTenReviews found that the 7z compression was at least 17% better than ZIP,[17] and 7-Zip's own site has since 2002 reported that while compression ratio results are very dependent upon the data used for the tests, "Usually, 7-Zip compresses to 7z format 30–70% better than to zip format, and 7-Zip compresses to zip format 2–10% better than most other zip-compatible programs."[18]
The 7z file format specification is distributed with the program's source code, in the "doc" sub-directory.
7-Zip can open some MSI files, allowing access to the meta-files within along with the main contents. Some Microsoft CAB (LZX compression) and NSIS (LZMA) installer formats can be opened. Similarly, some Microsoft executable programs (.EXEs) that are self-extracting archives or otherwise contain archived content (e.g., some setup files) may be opened as archives.
When compressing ZIP or gzip files, 7-Zip uses its own DEFLATE encoder, which may achieve higher compression, but at lower speed, than the more common zlib DEFLATE implementation. The 7-Zip deflate encoder implementation is available separately as part of the AdvanceCOMP suite of tools.
The decompression engine for RAR archives was developed using freely available source code of the unRAR program, which has a licensing restriction against creation of a RAR compressor. 7-Zip v15.06 and later support extraction of files in the RAR5 format.[20] Some backup systems use formats supported by archiving programs such as 7-Zip; e.g., some Android backups are in tar format, and can be extracted by archivers such as 7-Zip.[21]
Some forks add more formats.
File manager
7-Zip comes with a file manager along with the standard archiver tools. The file manager has a toolbar with options to create an archive, extract an archive, test an archive to detect errors, copy, move, and delete files, and open a file properties menu exclusive to 7-Zip. The file manager, by default, displays hidden files because it does not follow Windows Explorer's policies. The tabs show name, modification time, original and compressed sizes, attributes, and comments (4DOSdescript.ion format).
When going up one directory on the root, all drives, removable or internal appear. Going up again shows a list with four options:
Computer: loads the drives list
Documents: loads user's documents, usually at %UserProfile%\My Documents
Network: loads a list of all network clients connected
\\.: Same as "Computer" except loads the drives in low-level filesystem access. This results in critical drive files and deleted files still existing on the drive to appear. (NOTE: As of November 2020, access to the active partition in low-level mode is not allowed for currently unknown reasons.)
Features
7-Zip supports:
32 and 64-bit x86, ARM64 architecture
File Manager
Encryption via the 256-bit AES cipher, which can be enabled for both files and the 7z hierarchy. When the hierarchy is encrypted, users are required to supply a password to see the filenames contained within the archive. WinZip-developed Zip file AES encryption standard is also available in 7-Zip to encrypt ZIP archives with AES 256-bit, but it does not offer filename encryption as in 7z archives.[22]
Volumes of dynamically variable sizes, allowing use for backups on removable media such as writable CDs and DVDs
Opening EXE files as archives, allowing the decompression of data from inside many "Setup" or "Installer" or "Extract" type programs without having to launch them
Unpacking archives with corrupted filenames, renaming the files as required
Graphical user interface. The Windows version comes with its own GUI; however, p7zip uses the GUI of the Unix/Linux Archive Manager.[25]
Calculating checksums in the formats CRC-32, CRC-64, SHA-1, or SHA-256 for files on disk, available either via command line or Explorer's context menu[2]
Available in 89 languages
Ability to optionally record creation dates (tc) and last access dates (ta) in archives (in addition to modification dates).[26]
Versions
Two command-line versions are provided: 7z (7z.exe), using external libraries; and 7za (7za.exe), which is a standalone executable containing built-in modules, but with compression/decompression support limited to 7z, ZIP, gzip, bzip2, Z and tar formats. A 64-bit version is available, with support for large memory maps, leading to faster compression. All versions support multi-threading.
7-zip ZS is a fork with Zstandard and various other compression algorithms added to the file format.[27]
p7zip-zstd (p7zip with zstd) is p7zip with ZS additions.[28]
NanaZip is a fork integrating changes from many sources, modernized for the Microsoft Store.[29]
Plugins
7-zip comes with a plug-in system for expansion. The official "Links" page points to many plugins written by TC4Shell, providing extra file support.[30]
On older versions, self-extracting archives were vulnerable to arbitrary code execution through DLL hijacking: they load and run a DLL named UXTheme.dll, if it is in the same folder as the executable file.[32][33][34] 7-Zip 16.03 Release notes say that the installer and SFX modules have added protection against DLL preloading attack.[2]
Snapfiles.com in 2012 rated 7-Zip 4.5 stars out of 5, noting, "[its] interface and additional features are fairly basic, but the compression ratio is outstanding".[38]
On TechRepublic in 2009, Justin James found the detailed settings for Windows File Manager integration were "appreciated" and called the compression-decompression benchmark utility "neat". And though the archive dialog has settings that "will confound most users", he concluded: "7-Zip fits a nice niche in between the built-in Windows capabilities and the features of the paid products, and it is able to handle a large variety of file formats in the process."[39]
Between 2002 and 2024, 7-Zip was downloaded 428 million times from SourceForge alone.[40]
The software has received awards, In 2007, SourceForge granted it community choice awards for "Technical Design" and for "Best Project".[41] In 2013, Tom's Hardware conducted a compression speed test comparing 7-ZIP, MagicRAR, WinRAR, WinZip; they concluded that 7-ZIP beat out all the others with regards to compression speed, ratio, and size and awarded the software the 2013 Tom's Hardware Elite award.[42]
^Igor Pavlov. "7-Zip (home page)". 7-zip.org. Archived from the original on 21 January 2002. Statement on compression performance very similar in January 2002 and April 2017.
