March 21 (Reuters) - Google Inc's YouTube said 1 billion unique users were now visiting the video-sharing website every month, or nearly one out of every two people on the Internet.
"If YouTube were a country, we'd be the third largest in the world after China and India," YouTube said in a blog post on Wednesday.
Expanding high-speed data networks across the world and increased availability of internet-enabled smartphones have helped to connect billions of people to the Internet, fuelling growth in social media and video-sharing websites.
Facebook Inc reached 1 billion active users in September, a level of global penetration that has made its quest for sustained growth more challenging.
The popularity of music videos such as South Korean singer Psy's "Gangnam Style" has contributed to an explosion in viewership on YouTube. The video has so far clocked up 1.45 billion views.
YouTube was an instant success after its founding by three former PayPal employees in 2005, adding millions of users in its first year. Google bought it for $1.65 billion in 2006.
The fast-growing video site, which had about 800 million unique monthly users a year ago, now represents one of Google's key opportunities to generate new sources of revenue outside of its traditional internet search advertising business.
Google does not break out revenue from advertising on YouTube, which is a free site, but its contribution in terms of Google's overall revenue is relatively small.
AdAge reported in January that Google planned to offer paid subscriptions to some content later this year.
YouTube had reached out to several video producers, asking them to submit applications to create for-pay "channels," AdAge said, adding that the first such channels could be available by the second quarter for between $1 and $5 a month.