But social media conversations over the last 12 months have not all been about celebrities and music.
"Political expression and people expressing their opinions has been stronger than ever," European Twitter boss Bruce Daisley tells Newsbeat.
Daisley put Taylor Swift's global popularity in some perspective.
"She is the third biggest artist on Twitter. The second half of the year [saw] the Justin Bieber take-over of the world.
"Bieber is the second most followed, he had 50 million followers on Twitter from when he was a teen star and he has cleverly used that.
"Justin has reinvented himself using the power of social media. That's the genius of Bieber.
"He used a countdown with his fans, he used a wide fanbase of advocates and the social media amplified it."
Meanwhile, the most shared post of the year came from the One Direction frontman.
As statements go, it didn't say all that much - but you lot hit "retweet" in your millions.
Harry is not short of followers either - he is the most followed Briton with 26 million Twitter fans.
Twitter users were connecting more than ever over the big issues of the day, says Daisley.
"From the marriage equality movement in Ireland, through to Je suis Charlie in Paris, people more than ever used social media to show their solidarity to link up with other people."
The news in 2015 has often been very bleak, with terrorism and the refugee crisis two major talking points.
Daisley reckons that Twitter was the main way people identified with causes that mattered to them.
"We always wore poppies to express solidarity with people who have given their lives for us.
"I think the old phenomena are being transferred through to new social forms.
"So showing 'I support marriage equality' or showing that 'I'm against the savage attacks in Paris' is a 21 century digital poppy really."
Twitter's most followed
- Katy Perry - 78.3 million
- Justin Bieber - 70.5 million
- Taylor Swift - 66.7 million
- Barack Obama - 66.5 million
- Rihanna - 53.1 million