It took on average one second for Facebook.com to be displayed, even though the world's most popular social network had a couple of site outages in September, AlertSite said.
LinkedIn, designed for professional networking, ranked second with an average response time of 1.33 seconds, followed by YouTube (1.60 seconds), which was included because it has some social-networking capabilities.
Microblogging site Twitter (2.93 seconds) and social network MySpace (3.61 seconds) ranked fourth and fifth.
In terms of uptime, LinkedIn led the pack with 99.97 percent, followed by YouTube with 99.93 percent, MySpace (99.89 percent), Facebook (99.76 percent) and Twitter (99.74 percent).
Studies over the years have concluded that there is a direct relationship between the speed and reliability of a site and the level of usage and engagement it attains with its visitors.