Almost three quarters of U.S. Internet users watched some form of online video in September, and there appears to be little doubt about which site is serving up the most content.

A recent study from online metrics firm comScore found that Google's YouTube continues to dominate the growing online video market, accounting for 27.6 percent of the 9 billion videos that Americans watched on the Web in September.

About 70 million viewers watched those approximately 2.5 billion videos during the month, the report indicated. Google's other sites, such as Google Video, padded the company's runaway lead in online video by about 1.6 million.

Altogether, the search giant provided 28.3 percent of all online videos viewed in September. That averages to 6.3 times the number of videos served up by the second-most popular destination for online video.

In terms of market share, Google's closest competitors drop to the low single digits. Fox Interactive Media took the No. 2 spot, serving up 4.2 percent of online videos, followed by Yahoo sites with 4.1 percent.

Among the Fox properties, MySpace proved the biggest supplier of video content, serving up about 360 million videos that were seen by more than 38 million viewers. MySpace TV represented just a small part of its parent site's market share, claiming 766,000 viewers who watched 1.1 million videos.

The survey found that nearly three quarters of all U.S. Internet users watched either a streaming video or a progressive download video in September.

Google's lead in total content viewed stemmed in large part from repeat viewers, with its 71.6 million unique users watching around 2.5 billion videos. Fox Interactive Media grabbed 41.2 million unique viewers in total, followed by Yahoo, with 39.6 million.

On average, viewers watched 68 online videos per month, amounting to more than two a day.

The survey found that viewers on average watched just over three hours of online video content throughout the month, with an average video duration of 2.7 minutes.