The site is using artificial intelligence (AI) to verify the age of users on the app in a trial that currently only affects a small number of users in the US at present.

However, the trial could be rolled out more widely on the video app - which is owned by Google - should it prove successful.

It works by scanning users' activity on YouTube to figure out whether they are likely to be an adult or not.

Google's James Beser, who is in charge of product management at YouTube, said: "We will use AI to interpret a variety of signals that help us to determine whether a user is over or under 18.

"These signals include the types of videos a user is searching for, the categories of videos they have watched, or the longevity of the account."

Nothing will change for users if the site thinks they are adults but YouTube will automatically apply "age-appropriate experience and protections".

It means that personalised advertising will be turned off on the account and "digital wellbeing" tools will be activated.

The app will add safeguards to recommendations, including "limiting repetitive views of some kinds of content" and users will be prevented from watching content targeted at mature audiences.

Users will be able to prove their age to YouTube if they think they have been erroneously flagged as under 18.

Beser said: "If the system incorrectly estimates a user to be under 18, they will have the option to verify that they are 18 or over, such as using a credit card or a government ID.

"We will only allow users who have been inferred or verified as over 18 to view age-restricted content that may be inappropriate for young users."

Google has also confirmed that the user's registered birthday will not be taken into consideration as it is so often faked.

Beser explained: "This technology will allow us to infer a user's age and then use the signal, regardless of the birthday in the account, to deliver our age-appropriate product experiences and protections."