Facebook is finally adding a dislike button

Facebook will finally let its billion-plus users worldwide express displeasure or sadness about posts on the social service.

The company is developing a way for people to indicate a feeling of sadness or sympathy about Facebook posts, CEO Mark Zuckerberg revealed during a Q&A session Tuesday. That will complement the Facebook's trademark "like" feature, which it launched in early 2009.

After years of users asking for a "dislike" button, "today is the day I can say we're working on it and shipping it," he said at the live-streamed event.

Zuckerberg added that what Facebook users "really want is an ability to express empathy." He didn't provide details on when the feature would go live.