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Six new emoji with various expressions, from surprise to anger, join the “like” icon.Credit Facebook

SAN FRANCISCO — Despite the billions of “likes” bestowed on Facebook posts every month, something has been missing: an option to express a different emotion.

On Thursday, Facebook announced it will begin testing six new emotional reactions that you can convey with a simple emoji, similar to the thumbs-up “like” icon that the social networking service has made so famous.

The six new emoji depict various expressions, from an open mouth to express surprise to a scowling red face for anger. The other four emotions are love, laughter, sadness and a supportive cheer.

The new reaction icons will be available to most Facebook users in Spain and Ireland by the end of this week. Adam Mosseri, who oversees Facebook’s news feed, said the company would evaluate how people in those two countries use the new buttons and refine them, before expanding the rollout to the company’s 1.5 billion users worldwide later this year.

“How do people use it? Is this the right set of reactions?” Mr. Mosseri said in an interview.

Mark E. Zuckerberg, Facebook’s co-founder and chief executive, said last month that the company planned to test a way to “dislike” a post. “I do think it’s important to give people more options than just like,” he said at that time.

While none of the new buttons are labeled that way, the angry and sad faces are designed to express negative emotions in a sympathetic way.

Almost since the arrival of the like button, Facebook users have been asking for a dislike button or another quick way to express an opinion about a post beyond simply liking it. As more and more Facebook usage shifted to mobile phones, where typing comments is more difficult, it increased pressure on the company to introduce other reaction buttons.

Mr. Mosseri said that Facebook chose which emotions to add by looking at which virtual stickers people used most frequently in comments on posts.

And it was also important to pick emotions and emoji that translated well globally. “We tried the find the ones that are most universally used,” he said.