SAN FRANCISCO — Google Inc., owner of the world’s most popular search engine, unveiled a faster Internet search feature that gives users results as they type in requests.

Google Instant saves 2 to 5 seconds per search and will be available Wednesday on Chrome, Firefox, Safari and Internet Explorer 8 browsers in the United States, Vice President Marissa Mayer said at a media event here. A mobile version should be rolling out in the next few months, she said.

The company is making the upgrades to keep its lead in the $12.4 billion U.S. market for search-related advertising and stave off competition from Microsoft and Yahoo. Google had 65.8 percent of U.S. searches in July, down from 66.2 percent in June, according to ComScore Inc. Yahoo added share, while Microsoft’s Bing held steady.

The service “is going to draw more users and more activity and that is going to be good for us, for advertisers and, most importantly, for users themselves,” Google co-founder Sergey Brin said in an interview at the event.

The feature also changes text search ads while users type — a shift that will help marketers get more relevant ads in front of consumers, according to Jason Hennessey, director of search engine optimization at EverSpark Interactive, a search marketing consultant.

“The person saving several seconds for every search, that’s more time they can be spending on pay-per-click ads,” said Hennessey.

Google gets the bulk of its revenue from how many times Web users click on ads.

The service not only gives instant results but predicts what users want to search for with a series of suggestions. Users can select a suggested query without further typing. Those who prefer not to use the feature can turn it off.

Google Instant will also be offered to users in France, Germany, Italy, Russia, Spain and Britain who have capable browsers, Mayer wrote in a blog post. The company is working on rolling it out to all platforms and regions in the coming months, she said.