Windows Imaging Format: Difference between revisions

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| magic = {{mono|MSWIM\0\0\0}} / {{mono|WLPWM\0\0\0}} for wimlib [[Pipeline (Unix)|pipable]] variant<ref name="wimcapture">{{cite web|url=https://wimlib.net/man1/wimcapture.html|title=WIMCAPTURE|language=en|date=2018-11-24|access-date=2019-03-10}}</ref>

}}

The '''Windows Imaging Format''' ('''WIM''') is a [[Computer file|file]]-based [[disk image]] [[file format|format]]. It was developed by [[Microsoft]] to help deploy [[Windows Vista]] and subsequent versions of the [[Windows]] [[operating system]] family, as well as [[Windows Fundamentals for Legacy PCs]].<ref>{{cite web|url=https://technet.microsoft.com/en-us/library/dd799284%28v=ws.10%29.aspx|title=Windows Imaging File Format (WIM)|publisher=[[Microsoft]]|access-date=24 Feb 2014}}</ref>

== Design ==

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WIM supports three families of [[LZ77]]-based compression algorithms in ascending ratio and descending speed: XPRESS,<ref name=ms-xca>{{cite web | url=https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-xca/ | title=&#91;MS-XCA&#93;: Xpress Compression Algorithm | date=31 January 2023 }}</ref> [[LZX]], and LZMS.<ref name=wmilib-compression>[https://wimlib.net/compression.html wimlib: the open source Windows Imaging (WIM) library - Compression algorithm]</ref> The former two use [[Huffman encoding]], while the latter uses adaptive Huffman encoding with [[range coding]].<ref name=wimlib-compression-type>{{cite web |last1=Biggers |first1=Eric |title=wimlib_compression_type |url=https://wimlib.net/apidoc/group__G__general.html#gaf713fb36023a651f206a546e645ad09e |website=Wimlib documentation |access-date=2 October 2019}}</ref> There is also support for [[solid compression]]. Both solid compression and LZMS are introduced more recently, in WIMGAPI from Windows 8 and [[DISM]] from Windows 8.1.<ref>{{cite web |last1=Biggers |first1=Eric |title=WIMLIB_WRITE_FLAG_SOLID |url=https://wimlib.net/apidoc/group__G__writing__and__overwriting__wims.html#gab40a17c158783415c4c0dfa0de8b740c |website=Wimlib documentation}}</ref>

WIM uses [[SHA-1]] algorithm to calculate checksum for whole archive.<ref> {{Cite web |title=assorted/documentation/Windows Imaging (WIM) file format.asciidoc at main · libyal/assorted |url=https://github.com/libyal/assorted/blob/main/documentation/Windows%20Imaging%20(WIM)%20file%20format.asciidoc |access-date=2025-04-13 |website=GitHub |language=en}}</ref>

== Tools ==

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=== DISM ===

{{Main|Windows Assessment and Deployment Kit}}

Deployment Image Service and Management Tool (DISM) is a tool introduced in Windows 7<ref name=DISM-WinITPro /> and Windows Server 2008 R2<ref name=DISM-WinITPro /> that can perform servicing tasks on a Windows installation image, be it an online image (i.e. the one the user is running) or an offline image within a folder or WIM file. Its features include mounting and unmounting images, querying installed device drivers in an offline image, and adding a device driver to an offline image.<ref name=DISM-WinITPro>{{cite web |url=http://windowsitpro.com/systems-management/q-whats-deployment-image-servicing-and-management-dism |title=Q. What's Deployment Image Servicing and Management (DISM)? |work=[[Windows IT Pro]] |publisher=[[Penton (company)|Penton]] |date=29 January 2010 |first=John |last=Savill}}</ref><ref>{{cite web|url=https://technet.microsoft.com/en-us/library/hh824821.aspx|title=Deployment Image Servicing and Management (DISM) Technical Reference|date=29 February 2012|access-date=6 Oct 2012|publisher=[[Microsoft]]}}</ref><ref>{{cite web |url=https://technet.microsoft.com/library/dd744566 |title=What Is Deployment Image Servicing and Management? |date=22 October 2009 |access-date=14 Dec 2012 |work=[[Microsoft TechNet]] |publisher=Microsoft}}</ref> It is now possible to repair with DISM any image using either a Windows Installation CD or [[Windows Update]].<ref>{{cite web|title=Repair a Windows Image - Technet - Microsoft|url=https://technet.microsoft.com/en-us/library/hh824869.aspx|website=[[Microsoft Technet]]|publisher=[[Microsoft]]|date=20 October 2013}}</ref>

Before Windows Server 2012 and Windows 8, DISM had incorporated the majority of ImageX functions but not all; ImageX was still needed for image capture and applying.<ref name=DISM-WinITPro /> However, DISM [[deprecated]] ImageX in Windows 8.<ref>{{cite web|title=What is DISM?|url=https://technet.microsoft.com/en-us/library/hh825236.aspx|website=[[Microsoft TechNet|TechNet]]|publisher=[[Microsoft]]|date=18 April 2014}}</ref>

Windows 8.1 added ability to apply and capture disk images, and Windows 10 extended image applying, by adding compression.

Before Windows Server 2012 and Windows 8, DISM had incorporated the majority of ImageX functions but not all; ImageX was still needed for image capture.<ref name=DISM-WinITPro /> However, DISM [[deprecated]] ImageX in Windows 8.<ref>{{cite web|title=What is DISM?|url=https://technet.microsoft.com/en-us/library/hh825236.aspx|website=[[Microsoft TechNet|TechNet]]|publisher=[[Microsoft]]|date=18 April 2014}}</ref>

=== {{anchor|wimlib}} Support in other operating systems ===