YouTube will remove “unskippable” 30-second ads on the video-streaming service from 2018.

Long unskippable ads 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.

YouTube said that it wanted to “focus on formats that work well for both users and advertisers”, The Verge reported.

However, 15 and 20-second ads will remain. It is expected that the 30-second format will be replaced by YouTube’s new 6-second “bumper ad” format.

The 6-second bumper ads were introduced in 2016 and are designed to go better with shorter videos, which are increasingly being watched on mobile devices.