YouTube is to scrap "unskippable" 30-second advertisements on the video-streaming service, from 2018.
Google confirmed the plan to the BBC's Newsround programme, saying it wanted to focus on "formats that work well for both users and advertisers".
Long unskippable adverts are seen as a nuisance by many viewers, and Google has introduced shorter formats.
One media agency said the move reflected the difference between online video and linear television services.
Many other websites, including the BBC's international offer, feature unskippable 30-second ads on video content.