The free service, which offers around 3,000 hours of TV programmes from the BBC, Channel 4 and Five, has been made publicly available after less than a month of a closed beta trial of 20,000 web users.
Similar to music-streaming service Spotify, the content available on SeeSaw is peppered with 60-second adverts that can not be skipped. Ikea, Diageo and Kraft are among the advertisers that have already signed up.
It was billed as a 'one-stop shop' for video content online and was expected to offer users more than 10,000 hours of TV, with around 90 percent available for free and the rest available for rent or purchase.
However, the Competition Commission rejected plans for the service last year, saying it wouldn't benefit viewers.
A premium service, which will see web users 'rent' TV shows for 48 hours without any adverts, is expected to be rolled out in the next few months
Seesaw's platform controller, John Keeling, told BBC News: "I can see the comparison but Spotify is more of a free and subscription hybrid - we're looking at free and transactional pay-per-view hybrid."
Keeling added the service was in negotiations with a number of US companies regrading offering content on the service.