MENLO PARK, Calif. — Google unveiled a big revamp of its search engine Thursday that affects 90 percent of the search results served up worldwide by the Internet giant.

Called Hummingbird internally, the change to Google’s main search algorithm kicked in about a month ago, but was not disclosed by Google until Thursday at an event in Silicon Valley marking the company’s 15 year anniversary.

“It is really big,” said Google search executive Amit Singhal at the event.

The new algorithm makes search results more relevant and useful, especially when users ask more complex questions — something that has been happening a lot more in recent years, Singhal explained.

Google unveiled the change at the old Menlo Park, Calif., house of Susan Wojcicki, senior vice president of Google advertising. Google started in 1998 in Wojcicki’s garage and the company opened the space for reporters to announce its latest search efforts.

“We think about having 100 years to create the most amazing search opportunity. So we are 15 years in,” Wojcicki said Thursday.

Google dominates the multibillion dollar web search business, so any changes the company makes to its search business are closely watched, especially by those in the Internet and advertising industries.

Google revolutionized search by developing the PageRank system for ranking the world’s web pages based on relevance, using an algorithm that tracked how many times those pages are referenced by other pages. In 2010, Google completely changed the system through an upgrade called Caffeine — and now the company has re-built it again with Hummingbird.

The change comes as people become more comfortable asking long, complex questions when they use Google to search the web, rather than single words or simple phrases, Singhal explained in an interview with USA TODAY.

Google is also making the change to ensure its search results work well with voice-based queries. When people speak, rather than type on a computer, they use more complex phrases and Google had to update its algorithm to handle that, Singhal said.

Voice-based search is becoming more important as people use smartphones more to find information, Singhal and other Google executives said Thursday.

source: usatoday