UUPMediaCreator: building Windows install media from Microsoft's Unified Update Platform

Two tools with different jobs

UUPMediaCreator is a set of tools, not a single program, and the split matters when you plan an installation.

UUPDownload scans and fetches updates from Microsoft's own Unified Update Platform, and the README lists the product families it covers as Windows Desktop, Windows 10X, Windows Holographic, Windows Server, Windows Mobile and Windows IoT. It also decrypts ESRP payloads, verifies downloaded payloads, and can sample available builds through the get-builds argument.

UUPMediaConverter takes a downloaded UUP update for Windows Desktop and turns it into a usable ISO image, which the README says can be used in a DVD reader from the last decade or simply mounted. The phrase "when an appropriate tool does not exist in the wild" is the project stating its motivation: this fills a gap where the usual Microsoft tooling does not offer a given edition.

So the pipeline is fetch, then convert, with the second step being the demanding one. Knowing that split early saves an evening of wondering why a download completed and no ISO appeared.

What works on which operating system

The README carries a support matrix, and it is the most useful part of the document for deciding whether the project fits your setup.

On all three platforms, Windows, Linux and macOS, you can download files from UUP, replay past downloads, decrypt ESRP payloads, verify downloaded payloads, sample available builds, convert desktop UUP files to an ISO for one base edition, do so without administrative privileges, use the CLI, and get ARM64 support. The README notes the ARM64 line works on the device associated with the Twitter handle @sinclairinat0r.

Windows alone can convert to an ISO for all possible editions, produce a preinstallation environment close to the original, and build an ISO with the CDImage Mastering Utility using UDF and a boot sector.

Linux and macOS instead build with mkisofs, which needs UDF and a boot sector, and the footnotes name the extra packages: genisoimage on Linux, cdrtools on macOS, and libfuse2 for Linux generally.

Three rows are marked unsupported everywhere: building Hololens, Mobile, 10X and IoT images, update file integration, and, with a promise attached, the ease of use of UUPDownload.

Extra packages for the Linux and macOS path

If you are on Linux or macOS and going for the mkisofs route, the README lists the exact install commands in its footnotes.

apt-get install genisoimage

That is the Linux requirement for mkisofs. The macOS equivalent uses Homebrew.

brew install cdrtools

And the general Linux dependency, which the footnote marks as needed on that platform.

apt-get install libfuse2

libfuse2 is worth calling out because it is a common stumbling block on recent Linux distributions, where the older FUSE package was split into versioned packages. If the tool fails early with a mount error on a current distribution, that library is the first thing to check.

On Windows none of these apply, since the ISO is built with the CDImage Mastering Utility and no third party image tool is needed.

Naming the channel, edition, architecture and language

UUPDownload is described in the README as "a little too complicated to use for some people", and the reference table of parameters explains why. A call is a set of flags naming the channel, the product edition, the version, the ring, the build branch, the channel identifier and the architecture.

A Windows 11 retail desktop call looks like this.

-s Professional -v 10.0.22621.1 -r Retail -b Retail -c ni_release -t [your architecture]

The same shape covers every row in the table: retail desktop, retail IoT, retail holographic, retail mobile, retail team and retail server, then release preview, beta, dev and canary for the relevant products. Windows 10 and Windows 11 retail share a shape but differ in the channel identifier, with Windows 10 on vb_release and Windows 11 on ni_release.

Two extra flags narrow the download. Appending -e with an edition name gets the files for one edition only, and appending -l with a language gets the files for one language only. For a large product family that is the difference between a download of a few gigabytes and one of a few hundred.

The trap is stated in the README under an Important heading. The -v parameter does not select which Windows version you want. It tells Windows Update which version of Windows you are currently running, and the parameters are read as a description of the running system.

Where UUPMediaCreator is the wrong tool

The first limitation is the product coverage, and the README marks it plainly: building Hololens, Mobile, 10X and IoT images is not supported on any platform. The download tool can reach those channels, but there is no converter for them, which is a strange half support that can waste time.

The second is update file integration, listed as unsupported everywhere. If the goal is to take an existing install image and roll updates into it, this project does not do that.

The third is the platform split for the conversion step. A single base edition converts on all three operating systems, but producing ISO images for every possible edition, the closer to original preinstallation environment and the CDImage build are Windows only. A Linux user producing an image for many editions has to find a Windows machine or accept the mkisofs output.

The fourth is the ease of use. The README lists UUPDownload ease of use as unsupported with a promise attached, and that promise is dated against a parameter reference from 2021-05-18. The project itself flags its own rough edges, which is unusual and useful.

The fifth is release cadence. The recent releases are v3.1.9.3 from 2024-11-27, v3.1.9.2 from 2023-12-07 and v3.1.9.1 from 2023-10-15. The last push was on 2026-04-13, so the repository is not archived and work continues, but the tagged builds trail the source by a long way.

How UUPMediaCreator compares to the Microsoft Media Creation Tool and Fido

The Microsoft Media Creation Tool is the obvious alternative and the difference in approach is decisive. Microsoft's tool is a graphical, wizard-driven installer that downloads the current public release of one Windows edition for the machine it runs on. It produces an ISO quickly and needs no arguments, but it gives no control over the build, the ring or the edition, and it will not produce a specific older build.

UUPMediaCreator inverts that. It gives precise control over branch, ring, build and edition, at the cost of requiring the reader to know Microsoft's internal channel identifiers and to assemble a command line correctly. It is the difference between a tool that fetches what exists now and a tool that fetches a named artefact.

Fido, by Rufus's project, is the third point of comparison and sits closer to UUPDownload's job than to the converter's. It resolves a download script from Microsoft and hands the result to a downloader, which is a lightweight way to get current ISOs for the common editions. It does not fetch arbitrary build branches or editions and does not convert a UUP set, so it answers a narrower question.

For an unattended or reproducible build, a scripted approach such as the one here is the only one of the three that can express "this edition, this branch, this build". For a one-off installation on one machine, Microsoft's own tool remains less work.

Licence, maintenance and the shape of the project

The licence is MIT, and the repository ships a LICENSE file, so the source can be read, modified and redistributed under the usual conditions. A PRIVACY_POLICY.md is present at the root of the repository, which is worth reading before pointing the download tool at anything, since it fetches from Microsoft endpoints.

The project is a .NET solution, UUPMediaCreator.sln, with sources under src/, documentation under docs/ and third party libraries under thirdparty/. The publishing scripts at the root are named by target platform: publish_linux_x64.cmd, publish_win_arm64.cmd and publish_win_x64.cmd. The winmds directory holds Windows metadata, which is what lets the tool work against the different product families.

On maintenance, the repository is not archived and the last push was on 2026-04-13. The README links downloads to a separate GitHub releases page under the gus33000 account rather than to the repository's own releases, and a CI workflow badge points at the same account. The README also credits Rafael Rivera and Lucas as major contributors, the latter for the AppX code for Nickel and beyond.

The upgrade story is a self-contained .NET build rather than a package manager dependency, so the practical cost of moving to a newer build is low, but the cost of being on an old build is a mismatch with the current UUP endpoints.

Editorial conclusion

UUPMediaCreator suits someone who needs an install image for a specific Windows edition that the normal media creation tooling no longer offers, and who is comfortable with a command line and an overnight download. It is the wrong tool for everyday Windows installation, for a Hololens, Mobile, IoT or 10X image, since the README marks those as unsupported, and for anyone who needs update file integration into an existing image. Before relying on it, check which edition your conversion path supports on your operating system, since only Windows can produce all-edition ISO images, and read the -v parameter note, because the version number tells the tool which Windows you are running rather than which one you want.

Frequently asked questions

Official sources

1. Issues
2. License: MIT
3. OSTooling/UUPMediaCreator on GitHub
4. README
5. Releases