CANNES – Now that it has turned advertisers on to its marketing tools, Twitter is snapping at the heels of the biggest online ad gorillas, according to industry data.

“When you’re talking about the digital landscape, there are four dominant players that everyone knows – Google, Yahoo, Facebook and Microsoft,” ZenithOptimedia global CEO Steve King told Beet.TV in this interview during Cannes Lions.

“Those four companies represent about $49 billion out of the $77 billion of ad spend that’s generated. In fifth place would be Twitter, but still some way behind those companies.”

Twitter has spent the last couple of years implementing its ad propositions including Promoted Tweets. Now, with recent big tie-ups announced with WPP and ZenithOptimedia owner Publicis, Cannes Lions 2013 – and ZenithOptimedia’s data – show Twitter emerging as a major vendor in the space.

“It’s rate of growth is much higher than the other companies – they’re a much more nascent player,” King added.

ZenithOptimedia’s latest advertising forecast again credits growth in social media and online video ad spend as the driver of a 20 percent jump in internet display  expenditure. Those two categories are forecast to pull 30 percent more money this year. Press release and executive summary here.