Let's start with a simple HTTPS request: getURL("https://www.google.com") We get an error of the form Error in curlPerform(curl = curl, .opts = opts, .encoding = .encoding) : SSL certificate problem, verify that the CA cert is OK. Details: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed Now, let's get the Certification Authority bundle. You can install this on your operating system in one of several ways, e.g. sudo apt-get install ca-certificates Alternatively, we can download the file cacert.pem from Next, we have to tell libcurl to use this. We do this via the cainfo option. getURL("https://www.google.com", cainfo = "cacert.pem") (We can get the real page by following the redirection with getURL("https://www.google.com", cainfo = "cacert.pem", follow = TRUE) ) The same applies to reading data from the R mailing list site at getURL("https://stat.ethz.ch/pipermail/r-help/") http://ademar.name/blog/2006/04/curl-ssl-certificate-problem-v.html http://secure.globalsign.net/cacert/sureserverEDU.pem http://curl.haxx.se/docs/caextract.html