The Pew Research Center survey showed 62 per cent of US adults get news on social media, and 18 per cent do so often.
That shows a growing role for social media as a news source. In 2012, based on a slightly different question, 49 percent of American adults reported seeing news on social media, Pew said.
According to the survey, 66 per cent of Facebook users get news on the site, as did 59 per cent of Twitter users and seven of 10 users of Reddit.
The survey comes with Facebook defending itself against allegations that it suppressed some conservative news content in its "trending" topics.
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Last week, Facebook said was unable to substantiate any specific accusations of bias, but announced it was updating guidelines to be clearer that content decisions may not be based on politics or ideology.
Facebook founder Mark Zuckerberg met with a group of conservative political leaders and told them the network was "a platform for all ideas."
According to the new Pew study, users of Facebook YouTube and Instagram are more likely to get their news by chance, when they are online doing other things.
However, those who use Reddit, Twitter and LinkedIn often seek out news online as often as they stumble upon it.
In coordination with the John S and James L Knight Foundation, Pew surveyed 4,654 American adults by mail and online from January 12 to February 8. The margin of error for the full group was estimated at 2.4 percentage points.