Windows 11 26H2 on the Microsoft Update Catalog: what you can download

You cannot download the Windows 11 26H2 upgrade itself from the Microsoft Update Catalog: Microsoft's KB5121794 article states the 26H2 enablement package is only available through Windows Update, WSUS and other release channels, and a catalog search for it returns no results.

What the catalog does carry is every 26H2 cumulative update, dynamic update and .NET update, as .msu and .cab files. This guide lists them, shows how to download and install them, and points to the right official route for the upgrade itself.

Where to get each 26H2 file

Match what you are trying to do to a row. Only the last three rows involve the Microsoft Update Catalog.

You want to	Official source	Why
Move a Windows 11 24H2 or 25H2 PC to 26H2	Settings > Windows Update, or WSUS for managed PCs	The enablement package KB5121794 is not published in the catalog
Clean install 26H2 or upgrade from 23H2 or Windows 10	Windows 11 ISO or Installation Assistant from microsoft.com/software-download/windows11	Microsoft's download page lists Windows 11 2026 Update, version 26H2 as the current release
Update a PC already on 26H2 without Windows Update	Microsoft Update Catalog: KB5124010 or KB5129195	Standalone cumulative update .msu files for x64 and Arm64
Bring 26H2 installation media up to date	Microsoft Update Catalog: Safe OS and Setup Dynamic Updates plus the latest cumulative update	Microsoft's Dynamic Update process uses these exact packages
Update .NET Framework on 26H2 offline	Microsoft Update Catalog: KB5126052	Cumulative Update for .NET Framework 3.5 and 4.8.1 for 26H2

There are several official ways to download and install 26H2, and the ISO route has its own official 26H2 ISO links.

Every Windows 11 26H2 package in the Microsoft Update Catalog

A catalog search for 26H2 on September 30, 2026 returns these packages, all dated September 29, 2026 unless noted. Sizes are as the catalog lists them.

KB	Catalog title (short)	Classification	x64 size	Arm64 size
KB5124010	2026-09 Cumulative Update Preview for Windows 11, version 26H2 (26300.9550)	Updates	4981.5 MB	4825.6 MB
KB5129195	2026-09 Cumulative Update for Windows 11, version 26H2 (26300.9457)	Security Updates	4933.5 MB	4770.5 MB
KB5126052	2026-09 Cumulative Update for .NET Framework 3.5 and 4.8.1 for Windows 11, version 26H2	Security Updates	92.3 MB	110.6 MB
KB5124015	2026-09 Safe OS Dynamic Update for Windows 11, version 26H2	Critical Updates	162.9 MB	191.8 MB
KB5125758	2026-09 Safe OS Dynamic Update for Windows 11, version 26H2	Critical Updates	174.4 MB	205.5 MB
KB5126056	2026-09 Setup Dynamic Update for Windows 11, version 26H2	Critical Updates	17.2 MB	16.8 MB
KB5127216	2026-09 Setup Dynamic Update for Windows 11, version 26H2	Critical Updates	17.5 MB	17.1 MB
KB5124008	2026-09 Cumulative Update for Windows 11, version 26H2 (26300.9445), dated September 8	Windows Insider Pre-Release	4934.9 MB	4771.5 MB
KB5120998	2026-08 Cumulative Update Preview for Windows 11, version 26H2 (26300.9278), dated August 27	Windows Insider Pre-Release	4960.7 MB	4796.9 MB

The last two rows are pre-release packages from the Insider Release Preview period. For a production PC, use KB5124010 or KB5129195. Every release is tracked in the 26H2 update history.

What you need before downloading

Check	Why it matters	Where to look
The PC is already on 26H2	The 26H2 cumulative updates service a 26H2 PC; they do not perform the version upgrade	Settings > System > About, Version
Processor type	The catalog has separate x64 and Arm64 packages	System type on the same About page
Checkpoint update KB5043080	Microsoft lists it as the checkpoint that must be installed before KB5124010 and KB5129195	The catalog's download window for the target update
About 5 GB free per cumulative update	Each 26H2 cumulative update is between 4.7 and 5.0 GB	The catalog's Size column
Administrator rights	DISM and Add-WindowsPackage need an elevated prompt	Your account type

Download a 26H2 update from the Microsoft Update Catalog

1. Open https://www.catalog.update.microsoft.com in a browser.
2. Search for KB5124010 26H2 to see only the 26H2 rows of the latest cumulative update.
3. Pick the row for your processor: for x64-based Systems or for arm64-based Systems.
4. Select Download on that row.
5. In the download window, save every .msu file it lists, including the KB5043080 checkpoint file, into one empty folder such as C:\Packages.

Microsoft asks that no other files sit in that folder. DISM scans it and installs any checkpoint it finds before the target update.

Install the downloaded .msu with DISM

Search the Start menu for Command Prompt, right-click it and select Run as administrator. Then run the command below with the file name you downloaded.

DISM /Online /Add-Package /PackagePath:C:\Packages\windows11.0-kb5124010-x64_95a6272121df38221bfafc90b50baa8ec3e5294e.msu

/Online targets the running copy of Windows. /Add-Package installs the .msu, and DISM installs the KB5043080 checkpoint from the same folder first. On Arm64, use the file windows11.0-kb5124010-arm64_4ecd910ae0627561f49824e032723628302cdd21.msu. The PowerShell equivalent is Add-WindowsPackage -Online -PackagePath "C:\Packages\<file name>.msu".

You should see: DISM finishes without an error. After you restart, the OS build reads 26300.9550.

Microsoft also documents a manual route: double-click each .msu file in order, checkpoint first, then KB5124010. For a mounted offline image, replace /Online with /Image:<mount folder>.

Refresh 26H2 installation media with catalog packages

Microsoft's Dynamic Update process uses catalog packages to bring an older ISO up to the current month. Use packages from the same month as the cumulative update; if a dynamic update is missing for that month, Microsoft says to use the most recent one.

1. Download the latest 26H2 cumulative update (with its checkpoint), a Safe OS Dynamic Update, a Setup Dynamic Update and the .NET cumulative update KB5126052 for your architecture.
2. In the recovery image (winre.wim), add the cumulative update, then the Safe OS Dynamic Update, then clean up and export it.
3. In each edition of install.wim, add the cumulative update, then add .NET and its cumulative update after cleanup, then export.
4. In boot.wim, add the cumulative update, clean up and export.
5. Expand the Setup Dynamic Update files into the media's \sources folder.
6. Copy the serviced boot manager files and the boot.stl file from WinPE to the new media.

Microsoft's full script and task order are on its Update Windows installation media with Dynamic Update page. Skipping boot.stl can leave media that fails to start with error 0xc0430001.

Enable new context menu redesign on Windows 11

The redesigned File Explorer context menu cannot be downloaded from the Microsoft Update Catalog, and Microsoft has not announced it as part of the 26H2 general availability release. Microsoft introduced it in Windows Insider Experimental build 26340.9212 on August 17, 2026 and is rolling it out gradually to Insiders in that channel. It promises less top-level clutter and a Settings page to choose what appears. No catalog package switches it on, so wait for Microsoft to ship it through Windows Update.

How to check the update installed

1. Restart the PC after DISM finishes.
2. Right-click Start and select Settings.
3. Select System, then About.
4. Under Windows specifications, confirm Version is 26H2 and OS build is 26300.9550 for KB5124010, or 26300.9457 for KB5129195.

Fix problems with 26H2 catalog downloads

The catalog returns no results for KB5121794

Microsoft does not publish the 26H2 enablement package in the catalog; its KB article lists it as available only through other release channels.

1. On a 24H2 or 25H2 PC, open Settings > Windows Update and turn on Get the latest updates as soon as they're available.
2. Install KB5124010 or a later cumulative update if Windows Update offers it.
3. Select Download & install when Windows 11, version 26H2 is available appears. Microsoft is rolling it out in phases, so the offer can take time.

Updated installation media fails to start with error 0xc0430001

The boot.stl file used for Secure Boot validation is missing from the media or does not match the image.

1. Use Microsoft's Update WinPE script to update the image, which Microsoft recommends.
2. Or copy boot.stl from the device's Windows\Boot\EFI folder to the matching folder on the installation media.
3. Make sure the boot.stl file matches the Windows version and architecture of the image.

A 25H2 PC still shows version 25H2 after installing a 26H2-titled update

Cumulative updates keep a PC on its version; only the enablement package changes 25H2 to 26H2.

1. Check Settings > System > About. Build 26200.9550 means KB5124010 installed correctly as a 25H2 update.
2. Get 26H2 through Settings > Windows Update when it is offered to the PC.

Frequently Asked Questions

Is Windows 11 26H2 in the Microsoft Update Catalog?

Partly. The catalog lists 26H2 cumulative updates, dynamic updates and a .NET update, but not the KB5121794 enablement package that upgrades a PC to 26H2. Microsoft delivers that package only through Windows Update, WSUS and managed deployment services.

Can I download KB5121794 as an .msu file?

No. Microsoft's KB5121794 article says the update is not available from the Microsoft Update Catalog, and a catalog search for KB5121794 returns no results. Use Windows Update on a 24H2 or 25H2 PC, or the 26H2 ISO from Microsoft's download page.

What is the latest Windows 11 26H2 update in the catalog?

KB5124010, the 2026-09 Cumulative Update Preview for Windows 11 version 26H2, build 26300.9550, dated September 29, 2026. It is about 4.9 GB for x64 and 4.8 GB for Arm64.

Why is the 26H2 cumulative update almost 5 GB?

Each catalog .msu carries the complete cumulative update, listed at 4.7 to 5.0 GB. Microsoft's KB article says a device that already installed earlier updates downloads and installs only the new updates in the package, which is why Windows Update usually moves far less data.

What is a checkpoint cumulative update?

Since Windows 11 24H2, a cumulative update can depend on an earlier checkpoint update that must be installed first. For the September 2026 updates, Microsoft names KB5043080. The catalog's Download button offers it alongside the target update.

Can I use the catalog on an Arm64 PC?

Yes. Every 26H2 cumulative update, dynamic update and .NET update in the catalog has an arm64-based Systems version. Pick the row that ends in for arm64-based Systems and install it the same way with DISM.

Do I need the catalog if Windows Update works?

No. Windows Update installs the same cumulative updates automatically. Microsoft describes the catalog as a listing of updates that can be distributed over a corporate network, so it suits offline PCs, image servicing and organisations running their own update distribution.