Timeline is a Facebook profile feature that displays a user’s entire history of photos, links, personal milestones and other things shared on Facebook in chronological order, making them accessible with a single click.

Timeline doesn't expose anything that wasn't available for sharing in the past. Many of those older posts had always been available. People could get to them by continually hitting "Older Posts," although most wouldn't have bothered. Timeline allows people to jump to the older material more quickly.

The feature has caused much controversy because it becomes mandatory on January 31, 2012 for all 800 million Facebook users.