Cabinet (or CAB) is an archive-file format for

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

that supports

lossless data compression Lossless compression is a class of data compression that allows the original data to be perfectly reconstructed from the compressed data with no loss of information. Lossless compression is possible because most real-world data exhibits statistic ...

and embedded

digital certificate In cryptography, a public key certificate, also known as a digital certificate or identity certificate, is an electronic document used to prove the validity of a Key authentication, public key. The certificate includes information about the key, i ...

s used for maintaining archive integrity. Cabinet files have .cab

filename extension A filename extension, file name extension or file extension is a suffix to the name of a computer file (e.g., .txt, .docx, .md). The extension indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...

s and are recognized by their first four bytes (also called their '' magic number'') ''MSCF''. Cabinet files were known originally as Diamond files.

Design

A CAB archive can contain up to 65535 ''folders'' (distinct to standard operating system directories), each of which can contain up to 65535 files for a maximum of 4294836225. Internally, each folder is treated as a single compressed block, which provides more efficient compression than individually compressing each file. Every entry in a folder has to be a file.Microsoft Cabinet Format
/ref> Due to this structure, it is not possible to store empty folders in CAB archives. The following shows an example a CAB file structure, demonstrating the relationship between folders and files: * CAB file ** First folder *** *** ** Second folder *** *** How paths should be handled is not specified in the CAB file format, leaving it to the software implementation: * Some affix file paths to filenames only, as if all files in a CAB archive are in a single folder.

IExpress IExpress, a component of Windows 2000 and later versions of the operating system, is used to create self-extracting packages from a set of files. Such packages can be used to install software. Overview IExpress (IEXPRESS.EXE) can be used for dis ...

works this way, as does Microsoft Windows Explorer, which can open CAB archives as a folder. * Some can store the paths, and upon extraction, create folders as necessary. and (tools from Microsoft Cabinet SDK) as well as and (third-party

open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

tools) work this way. * , only since version 6 (which is included from Windows Vista to above) can extract files to their paths. The previous versions don't do it. The CAB file format may employ the following

compression algorithm In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compressio ...

s: * DEFLATE: invented by

Phil Katz Phillip Walter Katz (November 3, 1962 – April 14, 2000) was a computer programmer best known as the co-creator of the Zip file format for data compression, and the author of PKZIP, a program for creating zip files that ran under DOS. A c ...

, the author of the

ZIP file format ZIP is an archive file format that supports lossless data compression. A ZIP file may contain one or more files or directories that may have been compressed. The ZIP file format permits a number of compression algorithms, though DEFLATE is th ...

(specifically, the MSZIP encapsulation) * Quantum compression: licensed from David Stafford, the author of the Quantum archiver (not available in all versions of makecab.exe/diamond.exe) * LZX: invented by

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and Tomi Poutanen, given to Microsoft when Forbes joined the company * NULL: stored A CAB archive can reserve empty spaces in the archive as well as for each file in the archive, for some application-specific uses like digital signatures or arbitrary data.

Implementations

supports creating CAB archive files using the makecab

command-line A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...

utility. It supports extracting the contents of a CAB archive files using

File Explorer File Explorer, previously known as Windows Explorer, is a file manager application that is included with releases of the Microsoft Windows operating system from Windows 95 onwards. It provides a graphical user interface for accessing the file ...

, Setup API, and using the command-line commands expand.exe,expand - Windows CMD - SS64.com
/ref> extract.exe and extrac32.exe.
/ref> Other well-known software with CAB archive support includes

WinZip WinZip is a trialware file archiver and compressor for Microsoft Windows, macOS, iOS and Android. It is developed by WinZip Computing (formerly Nico Mak Computing), which is owned by Corel Corporation. The program can create archives in Zip ...

WinRAR WinRAR is a trialware file archiver utility for Windows, developed by Eugene Roshal of win.rar GmbH. It can create and view archives in RAR (file format), RAR or Zip (file format), ZIP file formats, and unpack numerous archive file formats. To en ...

7-Zip 7-Zip is a free and open-source file 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. 7-Zip has its own archive format called 7z, ...

. The aforementioned cabextract is a common tool for Linux systems, but is only capable of extracting archives. The gcab tool however can both extract and create CAB archives. For a full list, see .

Uses

A variety of

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...

installation technologies use the CAB format: these include

Windows Installer Windows Installer (msiexec.exe, previously known as Microsoft Installer, codename Darwin) is a software component and application programming interface (API) of Microsoft Windows used for the installation, maintenance, and removal of software. ...

, Setup API, Device Installer, Theme Pack and AdvPack (used by

Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated IE or MSIE) is a series of graphical user interface, graphical web browsers developed by Microsoft which was used in the Microsoft Wind ...

to install

ActiveX ActiveX is a deprecated software framework created by Microsoft that adapts its earlier Component Object Model (COM) and Object Linking and Embedding (OLE) technologies for content downloaded from a network, particularly from the World Wide Web. ...

components). CAB files are also often associated with self-extracting programs like

where the executable program extracts the associated CAB file. CAB files are also sometimes embedded into other files. For example, MSI and MSU files usually include one or more embedded CAB files. Windows uses the cabinet format to archive its Component-Based Servicing (CBS) log, which is kept in the folder . A bug in the compression process can cause run-away generation of useless log files both in that folder and in , which can consume disk storage until completely filling the hard drive. Deletion of the files without following a specific procedure can cause the deleted files to be regenerated at an increased pace. On

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

systems, CAB archives are used by

fwupd fwupd is an open-source daemon for managing the installation of firmware updates on Linux-based systems, developed by GNOME maintainer Richard Hughes. It is designed primarily for servicing the Unified Extensible Firmware Interface (UEFI) firm ...

to distribute

firmware In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide h ...

updates from hardware vendors that can be flashed on

non-volatile memory Non-volatile memory (NVM) or non-volatile storage is a type of computer memory that can retain stored information even after power is removed. In contrast, volatile memory needs constant power in order to retain data. Non-volatile memory typic ...

Related formats

The .cab filename extension is also used by other installer programs (e.g.

InstallShield InstallShield is a proprietary software tool for creating installers or software packages. InstallShield is primarily used for installing software for Microsoft Windows desktop and server platforms, though it can also be used to manage software a ...

) for their own proprietary archiving formats. InstallShield uses

zlib zlib ( or "zeta-lib", ) is a software library used for data compression. zlib was written by Jean-loup Gailly and Mark Adler and is an abstraction of the DEFLATE compression algorithm used in their gzip file compression program. zlib is also ...

for compression (see Deflate), but their headers are not the same as for Microsoft CAB files so they are incompatible and cannot be manipulated or edited with the programs that are made for standard cabinet format. Specialized third-party utilities, such as Unshield, can extract this specific proprietary format. This format has a different magic number of . Windows CE installer uses a variant of Microsoft CAB format with a magic. The compression is typically NONE, but MSZIP can also be found. Microsoft Publisher has a "Pack and Go" feature that bundles a publisher document, together with all external links, into a CAB file with a .PUZ extension. These files are meant to be activated with a companion .EXE file which is distributed along with the .PUZ file. These files may be opened with any CAB file extraction program.

References

External links

Microsoft Cabinet SDK
– updated versions of these resources are available in the

Microsoft Windows SDK Microsoft Windows SDK, and its predecessors Platform SDK, and .NET Framework SDK, are software development kits (SDKs) from Microsoft that contain documentation, header files, libraries, samples and tools required to develop applications for Micr ...