YouTube clips that depict dangerous or emotionally distressing “pranks” have been banned from the platform.
The move comes in response to so-called “challenges” that have sometimes resulted in death or injury.
The Google-owned video sharing site said such material had “no place on YouTube”.
However, the firm appears to be failing to enforce its existing rules on harmful content.
A Buzzfeed report detailed how images depicting, or alluding to, bestiality were still appearing on the site – despite a pledge last April to remove the material.
Some of the videos had attracted many millions of views. YouTube said it “worked to aggressively enforce our monetisation policies to eliminate the incentive for this abuse”.
Experts have however argued that enforcing Youtube’s new rules on pranks may prove even more difficult, given ambiguity over what may or may not be considered harmful.