Anti-knife crime protesters smeared themselves with fake blood outside YouTube's London offices in protest at the Google company's alleged promotion of graphic content.
Britain has very tough gun laws and shootings across the country are relatively rare.
But knife crime has been a problem for much of the past decade -- particularly in poorer neighbourhoods of big cities such as London where gang violence remains a concern.
Activists have appealed to social media platforms, expressing concern at the amount of crime-related content.
YouTube "is a contributing factor," Elaine Donnellon, lead organiser for the Operation Shutdown campaign group, told AFP at a rally with around 20 other women. "They have blood on their hands."