The first server on the list of CRAN mirrors at CRAN - Mirrors is https://cloud.r-project.org/, which is described as "Automatic redirection to servers worldwide, currently sponsored by Posit".
Does that mean that it is not a mirror server per se, but just redirects the user to another server, presumably one geographically close to the user?
The reason I ask is because I routinely have to provide guidance on how to install R, and the people to which I am giving this guidance could be anywhere in the world. Usually, I say something like "go to CRAN - Mirrors and find the mirror closest to wherever you are in the world...". But if https://cloud.r-project.org/ does what I think it might do, I presumably can tell anyone from New Zealand to UK to New York to London to just go to https://cloud.r-project.org/ and that will automatically connect them to their closest server.
Not exactly, from what I gather it's actually a CDN, so the end-user doesn't directly interact with any mirror.
Currently, the majority of R users install packages from two unique mirrors: httpd://cloud.r-project.org and httpd://cran.rstudio.com. These two mirrors are actually CDNs that use many servers world-wide to distribute packages.
And more explanation of the CDN configuration (in the context of cran.rstudio.com) here:
The server itself is a virtual machine run by Amazon’s EC2 service, and it syncs with the main CRAN mirror in Austria once per day. When you contact http://cran.rstudio.com, however, you’re probably not talking to our CRAN mirror directly. That’s because we use Amazon CloudFront, a content delivery network, which automatically distributes the content to locations all over the world. When you try to download a package from the Rstudio cloud mirror, it’ll be retrieved from a local CloudFront cache instead of the CRAN mirror itself. That means that, no matter where you are in the world, the data doesn’t need to travel very far, and so is fast to download.
I'm not sure what the difference between cloud.r-project and cran.rstudio is, from the links above it looks like cran.r-project gathers statistics, maybe not cloud.rstudio.