Twitter usage among U.S. adults who go online is up to 18 percent in the latest Pew Research Center survey, a slight increase from 16 percent last summer.
The survey released Monday once again showed Twitter's popularity among people younger than 30, with 30 percent of "millennials" active on the site. Twitter is also twice as popular among blacks and Latinos as people described as white. Its usage is fairly even across income and education levels.
Twitter remains far behind Facebook. Pew reported in February that 67 percent of U.S. adults who go online visit Facebook.
Previous Pew surveys in the past year have reported 20 percent of online adults using LinkedIn, 15 percent on Pinterest, 13 percent on Instagram, 6 percent on Reddit and 6 percent on Tumblr.
"The upshot is that Facebook is clearly the dominant player in this space, but Twitter use is very comparable to that of sites like Pinterest and Instagram," Pew senior researcher Aaron Smith said in an email. "And around three times as many Americans use Twitter as use sites like Reddit or Tumblr."
Overall, 72 percent of people surveyed this spring who reported using the Internet said they had "used a social networking site like Facebook, LinkedIn or Google Plus." That's up from 64 percent two years ago when Pew's question referred examples such as "MySpace, Facebook or LinkedIn." Much of the growth has come from people in the 65-plus age range.
Explore further: Pew's fact tank studies American social networking