YouTube has started rolling out vertical adverts, directed at those mainly watching videos through the mobile apps.

These new adverts are similar to the standard video ads, but they're optimised for phones. Available as either Universe App or TrueView campaigns, the ads target viewers based on what they're watching.

According to Adweek, YouTube chief product officer Neal Mohan said that 70 per cent of YouTube's watch time comes from mobile viewers.

Mohan also used Hyundai as an example of a company using both vertical and horizontal ads. He said that the car manufacturer reported a 33 per cent lift in brand awareness and nearly a 12 per cent rise in brand consideration.

"It used to be that people would open up the app very quickly, get off the home feed and started watching a video. But now the watch time that’s generated by recommendations on the home feed has grown 10X over the last three years,” Mohan said.

“So, it’s the place where users are willing to discover new content... we think it’s a great place for advertisers to engage.”