Sorry if this is obvious, but I read the article and am still a bit unsure. If you use libcurl on the front end to download a file using this method - where does the file end up? Is it in the browsers memory? Is it piped through websockets to some backend service? Is it written to local disk using the newish file system API?

From the article

> What this code does is read an index file that contains the list of R packages from CRAN, and subsequently download the description files of the first 200 packages to the user home directory (which is actually a virtual filesystem in WebR [1]). > [1] https://docs.r-wasm.org/webr/latest/mounting.html

So I think it's a virtual filesystem in browser memory.

You might use a data URL to allow the file to be downloaded. Gemini gave me a recommendation on how to do this with this query.

https://www.google.com/search?q=use+data+url+to+download+fil...