The Internet search company Google set a record in May, as more than 1 billion people visited its various websites.

A company that measures Internet traffic, ComScore, says this is the first time a company has had that many “unique visitors,” a measure that ignores multiple visits from the same person.

The traffic is an 8 percent gain over the same month from a year ago, and nearly 100 million visitors ahead of the second-place company, Microsoft.

Facebook is in third place with around 700 million unique visitors.

Google gets revenue by selling advertising, so a huge number of visitors helps the firm's profits.

But the Wall Street Journal reports that a growing number of advertisers are interested in the amount of time visitors spend on a site, not just the number of viewers. The paper says Facebook visitors stay on the site longer and therefore are more likely to see advertisements placed there.