Eventually all profiles will switch to the new look. Timeline is also available on touch devices using m.Facebook.com and Facebook for Android.

If you've put embarrassing photos or posts on Facebook, you'll have seven days after switching to Timeline to prune them from your profile before Timeline becomes the default look on your profile page.

Facebook CEO Mark Zuckerberg has called Timeline a way to share life experiences, but it could also become a carrot for marketers and advertisers to target consumers based on their "likes" and devotion to certain brands as Facebook duels with Google+ and other social networks for advertising dollars, analysts say.

R. "Ray" Wang, CEO at Constellation Research, says Timeline should improve the user experience by adding detail and context to one's profile.

At the same time, Mr Wang cautions: "There's a growing concern among individuals that Facebook is driving individuals to trade their privacy for convenience without understanding the risks. Can individuals turn it off forever if Facebook still owns the data? What do you do to take yourself out of a Timeline? Is this the beginning of digital extortion?"