The goal of urlchecker is to run the URL checks from R 4.1 in older versions of R and automatically update URLs as needed.
It also uses concurrent requests, so is generally much faster than the URL checks from the tools package.
library(urlchecker)
# `url_check()` will check all URLs in a package, as is done by CRAN when
# submitting a package.
url_check("path/to/pkg")
# `url_update()` will check all URLs in a package, then update any 301
# redirects automatically to their new location.
url_update("path/to/pkg")