SAN FRANCISCO — Google is once again taking up arms in the browser wars, in the belief that people who use its Chrome Web browser will be more likely to keep using Google search.

The company is taking the battle to mainstream America with an ad campaign using the old-fashioned medium of prime-time TV to talk about the Web. The 90-second ads, which began Tuesday night, show off Chrome, which it introduced in 2008. “As people look for more cool and more interesting things on the Web, our business grows,” said Andy Berndt, vice president of the Google Creative Lab, which created the campaign with the ad agency Bartle Bogle Hegarty.

While Google captures two-thirds of online searches, Microsoft, whose Bing service has only 14 percent of searches, has its browsers on far more computers.

About 45 percent of computers use one of Microsoft’s Internet Explorer browsers, according to StatCounter, a Web analytics firm, while Chrome has only about 18 percent of the market. Internet Explorer’s share, however, is down from 53 percent a year ago, while Chrome’s share has climbed from 8 percent. Last year, the number of Chrome users tripled to 120 million, from 40 million, Google said. Firefox, a browser produced by Mozilla, has 30 percent of the market while Safari, Apple’s browser, has only 5 percent.