The process of adding new updates or features to a pre-existing Windows setup media is known as Slipstreaming. Using this method, you can keep your existing ISO images updated with the required language packs.

Add Language Packs to existing Windows ISO media Download and install Windows Assessment and Deployment Kit (WindowsADK) Download and extract Windows ISO Image Determine image Index Number Mount .WIM file using DISM Add language pack(s) Commit and dismount Covert extracted folder back to ISO image Closing words

Learn how to add Windows Cumulative Updates to existing ISO images. Before we begin, it would be helpful to understand the types of language packs Microsoft offers for Windows.

Add Language Packs to existing Windows ISO media

Adding language packs to existing ISO images is a step-by-step process. You can do so by performing the tasks below in the order it is given in, and you should have no problems doing so. Note: This method is applicable for both Windows 11 and Windows 10 ISO images.

Download and install Windows Assessment and Deployment Kit (WindowsADK)

WindowsADK is a tool used to aid in the deployment of Windows OS in bulk, or on a large number of devices. To learn more about WindowsADK, refer to this blog post. You can also download and install WindowsADK through the guide provided in the post. We suggest that you do so before proceeding forward to the next step. This is because WindowsADK provides certain elements that are required to push the language packs into existing ISO images, such as the “Windows Kits” folder that can be found in C:\Program Files (x86).

Download and extract Windows ISO Image

If you do not already have an ISO image to begin with, you can download Windows 10 ISO image here, and Windows 11 ISO image from here. Once downloaded, right-click on the ISO file and click Mount from the context menu. When mounted, copy its content to an empty folder. Alternatively, you can also extract the ISO image from the context menu (using WinRAR, etc.) directly into an empty folder. We have extracted the image to D:\Extract. Once done, you may now proceed to the next step.

Determine image Index Number

Usually, an ISO image contains multiple editions of the same Windows, such as Professional, Education, Home, etc. Each of these editions has its own index number. An index number is an integer associated with each of these editions, which is required later when updating the ISO image with new language packs. Hence, we must determine the index number for the edition you will be deploying in the future using this ISO. Launch the Command Prompt with administrative privileges, then use the following command to determine the index number for the OS: Replace with the complete path to where you extracted the ISO image. Here is an example of the command above: Note: Do not close the Command Prompt until the very end, as any work done will need to be performed all over again. Since we will be adding language packs to Windows 11 Pro, the index number we will be using is 6.

Mount .WIM file using DISM

The next step is to mount the extracted Install.wim file to an empty folder so that changes can be applied to it.

Create a new, empty folder where the ISO will be mounted:md Replace with the complete path where you wish to create an empty folder. Here is an example where we created a folder named “MountISO” in the root of the D drive:Next, you need to mount the install.wim file to this folder. For that, use the command below:DISM /Mount-Wim /wimfile:"\sources\install.wim" /index: /mountdir:"“Here is an example of the command, where we replaced with the complete path to where the ISO is extracted, with the index determined in the last phase, and with the complete path to the empty folder just created in the last step.

Now that the install.wim file has been mounted successfully, it is now time to move on to the next step.

Add language pack(s)

You should now be able to add language packs to the mounted .wim file. However, you must first download the .cab files for the language packs that are right for your operating system. You can download them from the internet directly. Once downloaded, proceed with the command shown below to mount the language pack(s) to your ISO: In the command above, replace with the complete path with the folder you had created earlier (to which the .wim file is mounted) and also replace <PathTo.CABLanguagePack> with the complete version of the downloaded language pack. Here is an example: You can now continue to add as many language packs as you like. Remember that more language packs mean the larger the footprint of the operating system.

Commit and dismount

Once the language packs have been incorporated into the .wim file, all that is left to do is save the changes and then dismount the install.wim file. Use the command given below to commit the changes and dismount. Replace  with the complete path of the folder where install.wim file is mounted. In our case, we will be using the following command: Note that this may take a few minutes and the Command Prompt may look like it is stuck. However, that is not the case. Please allow a few minutes to commit and dismount successfully.

Covert extracted folder back to ISO image

You may now convert the updated Windows files and folders back to an ISO image using third-party tools. Here is a guide on how to convert files and folders into ISO images.

Closing words

With lesser download volume and customized language preferences, updating an existing ISO image can be speedy. It eliminates the headache of installing multiple language packs on a number of computers later on.