LONDON — Scenes of pranks ranging from silly to hazardous have long been among YouTube’s most popular offerings. Now, after multiple reports of people putting themselves or others at risk by copying some of those stunts, the video-sharing service is clamping down on content that, in its view, depicts “dangerous challenges and pranks.”

On Tuesday, YouTube, a unit of Google, updated its policies “to make it clear” that challenges “that can cause death and/or have caused death in some instances,” pranks “with a perceived danger of serious physical injury” and anything that causes “children severe emotional distress” are not allowed on the site.

In a statement, YouTube said the update — which cited pranks involving home invasions or drive-by shootings as unacceptable — was a result of a routine review of its longstanding enforcement guidelines and an effort to better define what it allows users to post. Users whose videos are taken down over the next two months for violating the standards can appeal the removals.

“We heard feedback from creators that we could provide some clarity on certain community guidelines,” the statement said, “so we published materials detailing our policies against pranks that cause others to seriously fear for their safety or that cause serious emotional distress to children and vulnerable individuals.”