While there is no set length, most are relatively short, ranging from 315 minutes in length.
Canadian sci-fi-fantasy seriesSanctuarybegan in 2007 as an eight-webisode series released only through the internet.
It has the study group on their way to an Emmy party, riding in an Infiniti QX 56.
However, its not just in the US that webisodes are gaining popularity.
I think we now have to accept that online stuff isnt a spin-off anymore, he said.
It was watched by 2.5m people in its week of release.
What more storytelling do we need?
Back in 2006, one of the first cult TV series to offer online episodes was Heroes.
He says the shows producers consciously exploited a range of media beyond TV to sustain interest in the show.
Webisodes and indeed all other forms of online content clearly have an audience in these shows fans.
Do some work better than others?
Yes, of course.
