San Francisco-based Twitter said it earned USD 91 million in the fourth quarter, the first positive net income since going public in 2013.
Revenue was up two percent from a year ago to a better- than-expected USD 732 million.
The number of monthly active users was 330 million, unchanged from the prior quarter but up four per cent from a year earlier.
While Twitter has built a solid core base of celebrities, politicians and journalists, it has failed to achieve the broader appeal of Facebook and other social platforms, hurting its ability to bring in ad revenues.
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The profitability is an important achievement for Twitter, which has lost money consistently since its public offering, sparking speculation on whether it needed to sell itself to keep operating.
Chief executive Jack Dorsey welcomed "a strong finish to the year," and added "I'm proud of the steady progress we made in 2017, and confident in our path ahead."
The network has stepped up efforts to boost its user base and engagement, adding streaming video partnerships, doubling the character limit on tweets to 280 and making it easier to create "tweetstorms" by stringing messaging together.
Jennifer Grygiel, a Syracuse University communications professor who follows social media, said the results are an important milestone for Twitter.
"It shows that Twitter has staying power," Grygiel said. "A lot of people have had doubts for several years."
Despite Twitter's problems these past few years, "it is unlike any other social media platform," Grygiel said.
"It really is the fastest newswire service we've ever seen," she said. "Influencers and news junkies come to Twitter because of that microblogging function that we don't see in other places."
Greenfield said Twitter's use of artificial intelligence had "made the Twitter user experience more compelling by showing consumers the tweets they care most."
Twitter's monthly user base of 330 million is far behind the two billion of Facebook, but Twitter said its daily active user base -- for which it has not offered a specific number -- grew in double digits.
"We are committed to making Twitter safer, and we are clarifying our policies, improving our enforcement, and communicating more clearly," the company said in a tweet.