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 using LZX, for fast compression using 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