Facebook's new 'Reactions,' which allows users to select from seven emotions including 'Angry', 'Sad' and 'Wow,' are now available to Facebook users worldwide. The extension of the "Like" button allow users to express emotions such as sadness, anger and love.

Facebook tasted "Reactions" in Ireland and Spain since October.

The company will also use "Reactions" to track user behavior and for ad delivery. "Reactions" would have the same impact on ad delivery as "likes".

"We will initially use any Reaction similar to a Like to infer that you want to see more of that type of content," Facebook said in blog post.

Facebook said that over time it hoped to learn how different "Reactions" should be weighted differently by the Facebook News Feed to customize it for individual users.

Twitter also replaced its star-shaped "favorite" icon with a heart-shaped icon called "like" in November.