What is CAB?

CAB (Cabinet) files are compressed archives used by Microsoft for distributing Windows system files, updates, drivers, and software packages. They use LZX or MSZIP compression algorithms and can span multiple volumes for large installations. CAB files support digital signatures for security verification, making them ideal for trusted software distribution. Windows includes built-in tools (expand.exe, extrac32.exe) for extracting CAB files.

CAB is used by Windows Update for system patches, driver installers (.inf + .cab), software setup programs, and embedded system images. Microsoft distributes DirectX, .NET Framework, and Windows components as CAB archives. IT professionals encounter CAB files when deploying Windows images, installing drivers, and managing updates. The format is deeply integrated into Windows installation and update infrastructure.

Did you know? Windows Update downloads millions of CAB files daily for system updates!

History

Microsoft developed Cabinet format to efficiently distribute software on floppy disks and later for Windows updates and system file distribution.

Key Milestones

  • 1996: CAB format introduced
  • 1998: Windows 98 uses CAB extensively
  • 2000: Windows Update adoption
  • 2006: Vista driver packages
  • 2015: Windows 10 update system
  • Present: Core Windows infrastructure

Key Features

Core Capabilities

  • LZX Compression: Efficient algorithm
  • Digital Signatures: Security verification
  • Multi-Volume: Spanning support
  • Self-Extracting: Executable CABs
  • Windows Native: Built-in support
  • Folder Structure: Preserved hierarchy

Common Use Cases

Windows Update

System patches

Drivers

Hardware driver packages

Installers

Software distribution

System Files

Windows components

Advantages

  • Native Windows support
  • Good compression ratio
  • Digital signature support
  • Multi-volume capability
  • Trusted by Windows
  • Preserves file attributes
  • Self-extracting options

Disadvantages

  • Windows-specific format
  • Limited cross-platform support
  • Proprietary Microsoft format
  • Complex extraction on non-Windows
  • Not user-friendly for general archives
  • Slower than ZIP

Technical Information

Format Specifications

Specification Details
File Extension .cab
MIME Type application/vnd.ms-cab-compressed
Compression LZX, MSZIP, or none
Platform Windows (primarily)
Signing Authenticode support
Max File Size 2 GB per cabinet

Common Tools

  • Windows Built-in: expand.exe, extrac32.exe
  • Creation: makecab.exe, IExpress, WinRAR
  • Extraction: 7-Zip, WinZip, PeaZip
  • Analysis: CabArc, Universal Extractor