The curl() function provides a drop-in replacement for base url() with better performance and support for http 2.0, ssl (https://, ftps://), gzip, deflate and other libcurl goodies. This interface is implemented using the RConnection API in order to support incremental processing of both binary and text streams. If you are looking for a more-user-friendly http client, try the RCurl or httr packages instead.
Have a look at the vignette to get started!