Buoyed by mobile ads sales, Facebook reported $12.97 billion in revenue for the fourth quarter that ended December 31 -- up 47 per cent from $8.81 billion in the same period last year.

Mobile advertising revenue represented approximately 89 per cent of revenue for the fourth quarter -- up from nearly 84 per cent of advertising revenue in the fourth quarter of 2016.

Daily active users (DAUs) were 1.40 billion on average for December 2017 -- an increase of 14 per cent year-over-year.

Monthly active users (MAUs) were 2.13 billion as of December 31 -- an increase of 14 per cent year-over-year, the company said in a statement late on Wednesday.

"Last quarter, we made changes to show fewer viral videos to make sure people's time is well spent," said Mark Zuckerberg, Facebook founder and CEO.

"In total, we made changes that reduced time spent on Facebook by roughly 50 million hours every day. By focusing on meaningful connections, our community and business will be stronger over the long term," he added.

This is the first time Facebook reported a user count decline in the US and Canada region -- from 185 million to 184 million daily active users..

Facebook currently employs 25,105 people -- an increase of 47 per cent year-over-year.

"2017 was a strong year for Facebook, but it was also a hard one," Zuckerberg said.

"In 2018, we're focused on making sure Facebook isn't just fun to use, but also good for people's well-being and for society.

"We're doing this by encouraging meaningful connections between people rather than passive consumption of content," the Facebook CEO added.