Windows Imaging File Format (WIM)
This topic introduces the Microsoft Windows Imaging (WIM) file format. WIM is a file-based disk image format that was introduced in Windows Vista. WIM files are compressed packages that contain a number of related files. The format of a WIM file is optimized for maximum compression with LZX, for fast compression with XPRESS, or uncompressed.
For a complete technical description of WIM, see the Windows Imaging File Format (WIM) white paper.
WIM File Structure
A WIM file structure contains up to six types of resources: header, file resource, metadata resource, lookup table, XML data, and integrity table. The following illustration shows the general layout of a WIM file that contains two images.
WIM File Layout
WIM Header—Defines the content of the .wim file, including memory location of key resources (metadata resource, lookup table, XML data), and various .wim file attributes (version, size, compression type).
File Resources—A series of packages that contain captured data, such as source files.
Metadata Resource—Contains information about the files that you are capturing, including directory structure and file attributes. There is one metadata resource for each image in a .wim file.
Lookup Table—Contains the memory location of resource files in the .wim file.
XML Data—Contains additional data about the image.
Integrity Table—Contains security hash information that is used to verify an image’s integrity during an apply operation.