Thursday, August 6, 2026 From rOpenSci (https://ropensci.org/blog/2026/08/06/r-universe-winarm/). Except where otherwise noted, content on this site is licensed under the CC-BY license.
Attentive package authors already noticed something new in their r-universe page over the past few weeks: R-universe has quietly started building and checking packages for Windows ARM64.
R-universe has supported ARM64 on Linux and macOS for some time already, but not Windows. With this addition, packages are now built and checked on both x86_64 and ARM64 across all major operating systems, making the R ecosystem fully ARM ready.
The R-universe service is part of a broader community effort to bring the R ecosystem to Windows ARM64. This project builds on the work from Tomáš Kalibera, whose efforts laid much of the groundwork for modernizing R on Windows to support UCRT and ARM.
Among other things, the project provides daily builds of base R installers for Windows ARM64 (R-release, R-patched, and R-devel), built on GitHub Actions with the rtools45 toolchain. Because CRAN repositories do not have Windows ARM64 binaries yet, these installers are patched to install binary packages from R-universe instead, so install.packages() just works. There is nothing users need to configure.
Rolling this out on R-universe turned out to be a great way to find out which parts of the ecosystem were not quite ready for Windows on ARM. Some things that needed patching:
rjags and runjags for arm.x86_64-pc-windows-gnu target. The extendr project shipped a fix in extendr-api 0.8.2, and rustup now supports the aarch64-pc-windows-gnullvm target we need.-msse compiler flags (ARM chips do not do SSE) or autoconf scripts misdetecting the toolchain.For broken CRAN and Bioconductor packages we maintain a set of install-time patches, and we are in the process of upstreaming these fixes to the package maintainers. With these patches in place, the entire R ecosystem now builds on Windows ARM64. 🎉
The fact that everything builds does not yet guarantee that everything behaves exactly as expected. We would love help from users to find any loose ends. Hence if you are running Windows on ARM hardware, or you are using a Windows VM on MacOS, we would love for you to take this for a spin.
For package developers there several ways to test packages with compiled code on Windows ARM64. As mentioned, if your package is already on CRAN or BioConductor, you can find binaries and check results on R-universe at https://cran.r-universe.dev/{pkg} or https://bioc.r-universe.dev/{pkg}.
In addition, GitHub Actions provides free windows-11-arm runners, and the standard workflows from r-lib/actions support them out of the box.
This project is exactly one of the reasons for building the R-universe system. Besides providing an open space for developers to publish new software, it also serves as a versatile infrastructure that lets us experiment with new tooling and platforms to help move the ecosystem forward as a whole. Having an automated platform that continuously builds thousands of packages made it possible to find those missing pieces, fix them, and iterate quickly.
By identifying and fixing the main hurdles now, we want to help package authors address the problems before they hit end-users, and pave the way for a smooth introduction of Windows ARM64 support on mainstream repositories such as CRAN and Posit Package Manager when the time is ready.
