YouTube is experimenting with a new feature that allow to add notes on videos

YouTube is experimenting with a new feature, "Notes", which allows users to add extra context and information to videos. This feature is being introduced as an experiment and will initially be available to a limited number of users. 

The purpose of Notes is to help clarify any confusion or misunderstandings
that may arise from watching a video, such as if the song in the video is
a parody, or if the older footage is mistakenly presented as a current event. Users can use Notes to provide clarifications or explanations, and also to help prevent the spread of fake or incorrect information.

During the initial testing phase, a select group of users with an active YouTube channel in good standing will have access to this feature.
Users in the US will begin seeing "Notes" on videos in the coming weeks and months, as the feature continues to be refined and improved. During the initial pilot project, independent evaluators will assess the usefulness and accuracy of the notes. Based on their feedback, YouTube will refine its systems.

If the "Notes" are deemed useful feature after testing, they will be made publicly available. 

The company says about a new feature: "People come to YouTube to learn about the world. With the Notes feature, we can provide even more context and make videos more relevant and interesting."