Google took its biggest leap yet onto Facebook's turf on Tuesday, introducing a social networking service called the Google+ project -- which happens to look very much like Facebook.
The service, which will initially be available only to a select group of Google users who will soon be able to invite others, will let people share and discuss status updates, photos and links.
But the Google+ project will be different from Facebook in one significant way, which Google hopes will be enough to convince people to use yet another social networking service. It is designed for sharing with small groups -- like colleagues, college roommates or hiking friends -- instead of with all of a user's friends or the entire Web. It also offers group text messaging and video chat.
"In real life, we have walls and windows and I can speak to you knowing who's in the room, but in the online world, you get to a 'Share' box and you share with the whole world," said Bradley Horowitz, a vice president of product management at Google who is leading the company's social efforts with Vic Gundotra, a senior vice president of engineering.
The debut of Google+ will test whether Google can overcome its past flops in social networking, like Buzz and Orkut, and deal with one of the most pressing challenges facing the company.
At stake is Google's status as the most popular entry point to the Web. When people post on Facebook, which is mostly off-limits to search engines, Google loses valuable information that could benefit its Web search, advertising and other products.
Google+ may already be too late.
In May, 180 million people visited Google sites, including YouTube, versus 157.2 million on Facebook, according to comScore. But Facebook users looked at 103 billion pages and spent an average of 375 minutes on the site, while Google users viewed 46.3 billion pages and spent 231 minutes.
Advertisers pay close attention to those numbers, and to the fact that people increasingly turn to Facebook and other social sites like Twitter to ask questions they used to ask Google, like a recommendation for a restaurant or doctor, because they want more personalized answers.
Mr. Gundotra and Mr. Horowitz said that knowing more about individual Google users will improve all Google products, including ads, search, YouTube and maps, because Google will learn what people like and eventually be able to personalize those products.
"To think we could achieve Google's stated mission of organizing the world's information absent people would be ludicrous," Mr. Horowitz said.
But Google has been criticized for failing to understand the importance of social information on the Web until competitors like Facebook and Twitter had already leapt ahead. Part of the blame, analysts say, falls on Google's engineering-heavy culture, which values quantitative data and algorithms over more nuanced, touchy-feely pursuits like socializing.
Exhibit A is Buzz, a social sharing tool for Gmail users. It automatically included users' e-mail contacts in their Buzz network, setting off widespread criticism that Google invaded users' privacy and failed to understand that people's e-mail contacts are not necessarily their friends.
Google quickly changed the service so it did not automatically connect friends. In March, Google settled with the Federal Trade Commission over charges of deceptive privacy practices related to Buzz and agreed to 20 years of audits.
Mr. Gundotra and Mr. Horowitz, both of whom worked on Buzz, say they were chastened by the experience. They said Google+ grew out of those mistakes, because they realized how much people care about controlling the information they share.
And unlike its approach with Buzz, which was tested only by Google employees before its broad introduction to the public, Google is calling Google+ a project to emphasize that it is not a final product, saying it will undergo many changes to fix problems and introduce new features. Still, its new Web site, plus.google.com, is Google's most fully formed social networking tool yet.
Mr. Gundotra and Mr. Horowitz said they took pains to mimic people's relationships in real life and eliminate the social awkwardness that things like friend requests and oversharing can generate on other sites.
Google+ users will start by selecting people they know from their Gmail contacts (and from other services, once Google strikes deals with them). They can drag and drop friends' names into different groups, or circles, and give the circles titles, like "sisters" or "book club."
Unlike on Facebook, people do not have to agree to be friends with one another. They can receive someone's updates without sharing their own. Users can also view their Google+ page the way their friends see it, to ensure their bosses do not see pictures from Saturday night, for instance.
Google+ users will see a toolbar on top of any Google site they use, where they can click to share something or see updates from friends. Eventually, the toolbar could appear on other Web sites. Google+ will also improve the usefulness of other Google products that have not gained traction, like Latitude for sharing your location and +1 for giving a thumbs-up to a particular site in search results, the executives said.
When users visit their Google+ homepage, they see three columns and a stream of status updates in the middle that looks remarkably like Facebook. But Google said that besides an easier way to share with select groups, Google+ has several other features that distinguish it from competitors.
It offers high-definition group video chat, called Hangouts, that other members of a group can join as it is happening. Users can search a section called Sparks to see articles and videos from across the Web on certain topics, like recipes or Alzheimer's disease, and share them with relevant groups of friends.
And on the Google+ mobile app for Android phones and iPhones, people can chat with groups using a feature called Huddle. Photos and videos shot with cellphones are automatically uploaded to a private album, so Google+ users can quickly view and post them from their phones or later on a computer.
With these services, Google will compete with a host of start-ups, like Path for sharing with small groups, SocialEyes for video chat, Flipboard for articles on certain topics and GroupMe for group texting.
"The notion that online sharing is broken is not an insight that is unique to us," Mr. Horowitz said. "We have a way to bring in millions of users in a way that is challenging for a start-up."