Menlo Park, California — Facebook announced a new mobile application for Android phones that promises to “put people ahead of apps,” by showing photos and friends’ updates as the central feature of a smartphone’s homescreen.

The app, called Facebook Home, will arrive preinstalled on a new smartphone made by HTC, but it will also be available for other Android phones through the Google Play app store on April 12.

Facebook CEO Mark Zuckerberg promised a crowd of reporters and analysts that the software will “turn your Android phone into a great, simple social device.”

The new software also integrates text messaging and Facebook’s own messaging service in a feature called “Chat Heads” — which displays a small photo of the person sending a message — and lets users chat with friends without interrupting other functions or apps on the device.

While phones and computers have traditionally been designed around programs and apps, Zuckerberg said, the new software is “designed around people first.”

The new HTC phone, called First, will be sold through AT&T for $99 with a two-year contract, starting April 12. Zuckerberg said the app will be available for downloading onto a limited number of other Android phones in coming weeks, and the company hopes to release a tablet version in the next several months.

By making it easier for smartphone users to access Facebook’s services, the company is clearly hoping to deliver more mobile advertising to those users. “The deeper that Facebook can get its users engaged, ultimately the more ad revenue they can get,” said Clark Fredricksen, a vice president at the research firm eMarketer.

To start, the new Home software won’t show any advertising, Zuckerberg said. But when asked if ads may eventually appear in “cover feed,” the new feature that displays large photos and updates on the phone’s home screen, Zuckerberg answered succinctly: “Yup.”

Analysts said the new features are visually attractive and will likely appeal to many Facebook users. But since the software puts so much emphasis on photos and other content from friends on Facebook, it may turn off some people.

“There are some very passionate Facebook users. I think they’ll love this,” said Gartner tech analyst Brian Blau.

But for other people, added mobile tech expert Chris Jones of the Canalys research firm, “there are different levels of willingess to expose themselves to a particular app. Some people like to keep their home screens fairly plain. Some people want to see their own photos, not other peoples’ photos.”

Jones added, “I think a lot of people may be really reluctant to dive into this straightaway.”

Facebook has been working hard to expand its mobile services and its mobile ad business over the past year, after it was criticized last spring for making virtually no money off the growing number of users who access the social network on smartphones and tablets.

The company reported more than $300 million in mobile ad sales last quarter. Its share of the U.S. mobile advertising market grew from zero to nearly 10 percent in 2012, according to eMarketer, which estimates Facebook will garner 13 percent of the $7.3 billion spent on mobile ads in the United States this year.

That makes Facebook an increasing threat to its Internet rival and Android owner, Google, which still dominates the market because it shows more mobile ads when people use Google’s search engine and other services on both Android and Apple phones.

Facebook users are clearly mobile: More than half its 1 billion active members check the social network regularly on their smartphones or tablets. And at the end of last year, researchers at comScore estimated Facebook outpaced Google Maps as the most frequently used smartphone app in the United States.

But experts say the business of selling smartphones may be difficult to crack. HTC had little success with earlier phones that came with a Facebook “button” preinstalled, IDC analyst Will Stofega noted.

Zuckerberg has previously insisted he doesn’t want Facebook to build its own phone, since he wants the social network to be available on a variety of phones and operating systems. Facebook has also worked with Apple to make its services easier to use on new iPhones.

Brandon Bailey San Jose Mercury News

Contact Brandon Bailey at 408-920-5022; follow him at Twitter.com/brandonbailey