Google accounted for more than 68 percent of all search traffic in the United States, and for about 87 percent in the United Kingdom, according to data collected by Hitwise in May.

The online search giant reported year-over-year growth in both countries.

Its biggest rival Yahoo, however, made up 20 percent of all U.S. search traffic, which was relatively flat year-over-year. In the United Kingdom, its search traffic dropped to four percent, from nearly nine percent in May last year.

Microsoft's search traffic declined year-over-year both in the United States and United Kingdom. U.S. raffic to Ask.com increased slightly, but slipped in the United Kingdom, Media Post reported.