The average U.S. Internet user watched about 16.8 hours of online video in June 2011, up from 14.5 hours a year ago, with a total of 178 million Americans watching a record 6.26 billion sessions in the most recent month, according to research firm comScore.
The length of the average video session was 5.4 minutes in June 2011, up from 4.9 minutes a year ago, while the average online video ad stayed the same at about 0.4 minutes.
YouTube and other Google sites retained the No. 1 spot, with 149.3 million unique viewers who watched 2.3 billion videos. Music-video site Vevo was next with 63.0 million viewers, followed by Yahoo at 52.7 million, Microsoft at 50.7 million, Viacom Digital with 49.5 million and Facebook with 47.7 million.
Hulu -- in the process of being sold by its owners, NBC Universal, Walt Disney Co. and News Corp. -- ranked ninth on unique viewers, with 26.7 million. Hulu served about 1 billion ads accounting for about 19% of the 5.3 billion total U.S. online video ads viewed in June 2011, comScore said. Hulu also delivered the highest frequency of video ads to its viewers with an average of 38.8 per viewer over the course of the month, more than three times the next highest property (which was Tremor Media Video, at 12.1 per viewer).
Video ads accounted for 13.6% of all videos viewed but only 1.3% of all minutes spent viewing video online. The top video ad networks for June 2011 in terms of their reach of the total U.S. population were: Tremor Media at 44.3%, BrightRoll Video Network at 38.5% and Break Media at 37.6%.
The overall number of U.S. online video viewers increased only slightly, from 177.5 million last year to 178.4 million in June 2011, according to the research firm.