Twitter Inc., the social-networking site that lets people share 140-character messages, is now used by 13 percent of adults online, up from 8 percent in November 2010, according to a report today by Pew Research Center.

Among Twitter users who own cell phones, 54 percent have used the mobile devices to access the social-media service, the report found. Additionally, Twitter use has more than doubled since late 2010 among people ages 25-34, to 19 percent from 9 percent, and increased among adults ages 35-44, to 14 percent from 8 percent.

The San Francisco-based company is increasingly counting on advertising, which can command higher rates with higher usage of the site. Twitter’s surging prospects and potential ad revenue have helped drive up its valuation. It was valued at $3.7 billion in December when it received an investment led by venture-capital firm Kleiner Perkins Caufield & Byers.