Facebook says its latest product, which displays updates and photos on Android screens, is built around people not apps.
Facebook has stopped short of developing its own mobile phone, instead launching a new product it says will allow Android devices to be built around people, not apps.
The software, called Home, was unveiled at an event in California by the company’s co-founder Mark Zuckerburg.
Features include Cover Feed, which replaces the traditional Android home screen and allows users to swipe through photos and status updates posted by their contacts.
Chat Heads let users interact with their friends while using other apps, which are accessed through Facebook’s new App Launcher.
Facebook had been rumoured to have been developing its own smartphone, but Mr Zuckerburg insisted that would be “the wrong strategy”.
“We’re not building a phone or an operating system but we are building something that’s much deeper than an ordinary app,” he said.
“The home screen is the soul of the phone. You look at it about 100 times a day and it sets the tone for your whole experience. We think it should be deeply personal.”
For Facebook, bolstering its mobile presence is crucial.
Chat Heads allow users to speak to their friends while accessing other apps
Nearly 70% of its one billion members use smartphones and tablets to access the service, while 157 million people log on solely from mobile devices.
Shares in the company, which is listed on the NASDAQ stock exchange, climbed around 3% to $27.03 (£17.81) within an hour of the launch at its Menlo Park headquarters.
Technology analyst Zeus Kerravala described Facebook Home as “an interesting idea”, adding: “If anyone can pull it off Facebook can.”
He said: “People spend more time on Facebook than on any other app so a device with the look and feel of Facebook, I imagine, will be hugely popular.
“What Facebook has had trouble with is monetising mobile – what they can push to users and when. That is what Wall Street has been critical of.”
Jeff Chester, executive director of the Centre for Digital Democracy, warned that Facebook users should be aware of how much information they are handing over.
“Rather than merely looking in on our data, as they do with an app, this will give Facebook much greater control of that data,” he said.
“Geo-locating technology is what it is all about right now. It is that data they need for marketing and advertising and it is what they want to be able to show to Wall Street.”
Mr Chester said too many people were unaware of how much data the social network collects and, with mobile devices increasingly being used as electronic wallets, people should be concerned about the trail of information they leave.
He added: “We might not mind them knowing what books we have bought but what if your mobile device is revealing medical information, such as what you’re buying in a pharmacy? I believe there will be a backlash.”
HTC First, a new phone built around Facebook Home, will be the first device to be pre-loaded with the software.