SINGAPORE - A sheep that breathed fire after chewing on extremely spicy Korean fried chicken is the star of one of the best performing ads on YouTube, a 6-second example of how mobile has changed online advertising.

Six seconds is a "nice meeting place" for advertisers to convey their message to customers who may not have time to view long ads, said Mel Silva, managing director for go to market strategy and operations at Google Asia-Pacific.

"People are using stolen moments to watch some content," Silva told reporters at the Growing with Google business forum here.

"What digital has done is create the ability for more people to watch more short-term content," she said.

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Knowing exactly what the advertiser wants to achieve and the target audience is at the core of any marketing campaign, regardless of format or length in case of video, Silva said.

App developers for example, should determine whether their campaign is aimed at encouraging more app downloads or purchases within the app, she said.

People binge-watching on Netflix dispel the notion that people are only interested in short video, she said.

"What is different are the cultural nuances," she said. "Universally, great campaigns are targeted at the right audience and they're engaging and they help you get something done."

In the Philippines, the best performing ads include the story of a lost dog and a dance tutorial featuring Jollibee fast food chain mascot. Both run for around 4 minutes.

YouTube has some 1.5 billion visitors monthly, Google said. The 6-second spots or "bumper ads" on the platform cannot be skipped, unlike other ads that are longer but can be skipped at the fourth second.

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Half of the world's nearly 3 billion internet users are in Asia. Android, Google's mobile operating software, is on 2 billion active devices.