FORTUNE -- Facebook's much-hyped mobile phone software, Home, has slipped into the world early.
Facebook's (fb) software will act as a launcher, taking over a user's Android phone and putting the social networking site's features front and center. In a public demonstration last week, Facebook executives showed off apps like Cover Feed, the equivalent of the News Feed that presents new photos and status updates on the first screen a user sees, and Chat Heads, allowing users to continue conversations even when they're working on something else.
Facebook Home is not the Facebook Operating System some have speculated about. Unlike Google, Apple (aapl), and Microsoft (goog), the company is not pouring resources into creating its own OS. Nor is it "forking" Google's Android OS -- that is, creating its own version of Android as Amazon (amzn) has for its Kindle tablets. "We are not going to totally rotate our company to build something that is only going to help out 3% of our people in a good case," Facebook CEO Mark Zuckerberg told Fortune in an exclusive interview.
Initially, Facebook Home will only be compatible with five handsets, but MoDaCo's website claims the leaked software can be made to operate on a wider range of devices such as Google's Nexus 4 phone and Nexus 7 tablet. At last week's announcement, Facebook executives said Home would be available on Android tablets at a later date.
Some of Home's most anticipated features do not appear to work in the pre-release software. The company's Chat Heads are one example. Another limitation: The maximum supported resolution is 1280 x 768. According to online accounts, getting the software to run at all is somewhat of a trial.