Download the Windows 11 26H2 ISO early with UUP Dump

Windows 11 26H2, the 2026 Update, is expected to start rolling out later in 2026, likely around September or October. Microsoft has not posted an official ISO for it yet, but you can still build one early from the preview builds using UUP Dump. This is the practical way to test a clean install or an in-place upgrade on a spare PC or a virtual machine while the release is still in development.

Quick answer: Open the UUP Dump 26H2 page, pick the latest 26300-series build, choose your language and editions, select “Download and convert to ISO,” enable “Include updates,” then run uup_download_windows.cmd as administrator. The finished 26H2 ISO appears in the extracted folder.

UUP Dump does not host any Windows files itself. It generates a small download package that pulls the required components straight from Microsoft’s update servers and packages them into an installation image on your machine. The resulting ISO is unofficial, but every file inside it comes from Microsoft, which makes it a dependable option for enthusiasts and testers.

Before you start: requirements and warnings

Treat 26H2 as test software. Preview builds can contain bugs, unfinished features, and unexpected issues, so install it on a spare device or virtual machine rather than your main PC. Back up anything important first.

About 70GB of free space on your primary drive for the script to download and process the files.
A reliable internet connection. The full process can take up to an hour depending on speed.
An 8GB or larger USB flash drive if you plan to install on real hardware.
The correct architecture: x64 for Intel and AMD systems, arm64 for Copilot+ PCs and other ARM devices.

Download the Windows 11 26H2 ISO with UUP Dump

Open the UUP Dump 26H2 page to see the latest 26300-series builds.

Select the “Windows 11, version 26H2” option for the latest x64 ISO, for example build 26300.8597 or any newer release. The build number changes over time, so pick the one with the highest number. If you have an ARM-based device, choose the arm64 architecture instead.

Use the “Language” drop-down to choose the language for your installation.

Click Next, then select the 26H2 editions you want included in the ISO. Click Next again.

Choose the “Download and convert to ISO” option.

UUP Dump download and convert 26H2 ISO script

Check the “Include updates (Windows converter only)” option. This integrates the cumulative updates so the script produces a true 26H2 image. Then click “Create download package” to save the tool to your computer.

Open the downloaded zip folder in File Explorer and click “Extract all.” Pick a location and click Extract.

Right-click the uup_download_windows.cmd batch file and choose “Run as administrator.” If Windows shows a security prompt, click “More info,” then “Run anyway” to begin.

Press the “R” key to run the script once, then press Enter. When the process finishes, press the “0” key to close the window.

The completed Windows 11 26H2 ISO will be saved inside the same folder where you extracted the UUP Dump files. You know it worked when the ISO file appears there with a 26300-series build number in its name.

Note: If the script fails, right-click Remove_Failure_MountDr_TempDir.cmd in the same folder and run it as administrator, then start UUP Dump again. Most failures come from running out of disk space, so confirm the drive has enough room before retrying.

Create a Windows 11 26H2 bootable USB with Rufus

Once you have the ISO, Rufus is the simplest way to write it to a USB drive for a clean install or an in-place upgrade. Connect a flash drive of at least 8GB before you start, since its contents will be erased.

Open the Rufus website and download the latest version under the Download section.

Double-click the rufus.x.xx.exe file to launch the tool.

Pick your USB flash drive from the drop-down under the “Device” section, then click Select.

Choose the Windows 11 26H2 ISO file and click Open. Then set “Image option” to “Standard Windows 11 Installation.”

Select GPT under “Partition scheme” and UEFI (non-CSM) under “Target system.” Give the drive a clear “Volume label” such as “Windows 11 26H2 Setup.”

Keep the default “File system” and “Cluster size” values. Check “Quick format” and “Create extended label and icon files,” then click Start.

If your PC already meets the Windows 11 requirements, clear all the checked customization options. To install on hardware that does not qualify, check “Remove requirement for 4GB+ RAM, Secure Boot and TPM 2.0” and “Remove requirement for an online Microsoft account.”

Click Start, then click OK to confirm that the USB drive will be wiped and the bootable media created. When Rufus reports “READY,” the drive is ready to install Windows 11 26H2.

Ventoy is a good alternative if you want to keep several ISO files on one drive by copying them over, and you can also build installation media with the Command Prompt.

Should you install 26H2 now?

For most people there is little reason to jump on 26H2 months before the public release. The appeal is narrow but real. If you want to preview upcoming changes, check whether your apps run on the new build, or start planning a deployment, building an ISO with UUP Dump is faster and more flexible than waiting for Microsoft to publish an official image.

The trade-off is stability. The earlier you grab a build relative to the final release, the more likely you are to hit rough edges. Keep these images on test hardware, hold off on your daily driver, and you get an early look at the 2026 Update without putting your main setup at risk.