Twitter Inc.’s ad revenue soared 126% year over year in the first quarter, but the social network still isn’t profitable.

Twitter continued refining in the first quarter the tools it offers advertisers. For example, Twitter launched its tailored audiences option to enable marketers to target their own customers.

However, the social network’s growth rate, 25% over the same period a year earlier, is much slower than other social networks such as Facebook-owned Instagram, which grew 100% year over year. 

For the first quarter ended March 31, Twitter reported:

• $226 million in ad revenue, up 126% from $100 million a year earlier.
• Ad revenue of $3.47 per 1000 views from U.S. users, up 77.9% from $1.95 in 2012.
• Ad revenue of 61 cents per 1000 views from international users, up 154.2% from 24 cents in 2012.
• $250.5 million in total revenue, up 119.2% from $114.3 million from the same period in 2013. 
• Mobile advertising accounted for roughly 80% of advertising revenue, or roughly $180.8 million, up from about 75% in the fourth quarter.
• 255 million monthly active users, up 25.0% from 204 million in the same period a year earlier.
• 198 million consumers, 77.6% of Twitter’s monthly active users, accessed Twitter from a mobile device.
• $132.4 million net loss, up from a $27.0 million loss a year earlier. Twitter attributes some of that loss to its acquisition of mobile-focused advertising firm MoPub.

“I’m proud of the speed with which the teams here integrated MoPub, our mobile ad exchange into Twitter,” said Twitter CEO Dick Costolo today during a conference call with analysts. “It now reaches over 1 billion iOS and Android users, making it one of, if not, the largest in-app mobile ad exchange and the only one at scale to offer publishers native in-app advertising.”