Google has become the first online operation to attract more than one billion visitors in a single month.
New figures by industry tracker comScore suggest that slightly more than 1bn people visited Google websites in May, in what has been billed as an unprecedented turn-out on the internet.
Microsoft websites were closing in on the milestone with about 900,000 unique visitors for the month, according to comScore.
Facebook had the third most visited web addresses, but topped other online venues in terms of how long people lingered after they arrived.
ComScore extrapolated the findings from a sampling of two million internet users.