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. A variety of Microsoft installation technologies use the CAB format - these include Windows Installer, Setup API, Device Installer and AdvPack. CAB files are also often associated with self-extracting programs like IExpress 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.
File structure
A CAB archive can contain up to 65535 CAB-folders, each can contain up to 65535 files. Internally, each CAB-folder is treated as a single compressed block, which provides more efficient compression than individually compressing each file. Every entry in a CAB-folder has to be a file. 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 CAB-folders and files: 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 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. CABARC.EXE and EXTRACT.EXE as well as lcab and cabextract work this way.
EXPAND.EXE, only since version 6 can extract files to their paths. The previous versions don't do it.
The expand command is used to uncompress one or more compressed.CAB cabinet files. It is also known as the Microsoft File Expansion Utility and dates back to MS-DOS 5 in 1990.
Display only the list of files in the archive:
C:\> expand -d archive.cab
extrac32
The extrac32 command is also used to uncompress one or more compressed.CAB cabinet files. It is part of Internet Explorer.
Extracting the archive archive.cab to the output folder:
C:\> extrac32.exe archive.cab /L "C:\output\"
makecab
The makecab command is used to create CAB archives:
Other well-known software with CAB archive support includes WinZip, WinRAR or 7-Zip. The aforementioned is the tool for GNU/Linux systems. However, fewer programs can create CAB archives. For a full list, see.
Related formats
The .cabfilename extension is also used by other installer programs for their own proprietary archiving formats. InstallShield uses zlib for compression, 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.
Windows uses the .cab format to archive its Component-Based Servicing log, which is kept in the folder C:\Windows\Logs\CBS. A bug in the compression process can cause run-away generation of useless log files both in that folder and in C:\Windows\Temp, 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.
