More than one in 10 UK on-demand and online video viewers over 16 have seen something that concerns them, with younger people who watch more on the web even more likely to have seen worrying content.

The proportion of viewers who have seen something that concerns them rises to 16% among 12- to 15-year-olds and 16- to 34-year-olds, the two groups who watch the most on-demand and online content, according to an Ofcom report.

The report says that 71% of all adults aged over 16 have watched online video or on-demand TV, rising to 94% among young adults between 16 and 24.

However, while 30% of adults who had seen concerning video online are concerned by sex, that fell to 23% among teens. Bad language and bullying or victimisation of themselves or others were more concerning for teens, with 37% saying those issues were a worry.

Parents were more likely to be concerned by on-demand than non-parents 17% v 8%), but were no more likely to find particular issues more worrying except when it came to pornography, where 22% said they were concerned, compared with 14% among viewers as a whole.

Ofcom says that awareness of reporting tools for content was higher with short-form video services such as YouTube than longer-form TV such as video-on-demand services from broadcasters. More than one in three of those surveyed said they were aware of how to report non-professional YouTube content, 26% said they knew how to report social network video content, and 23% said they were aware of how to report professional YouTube channels.

In comparison the only long-form video where awareness of reporting tools was comparable was TV catch-up, where 20% of adults knew what action to take.

Viewers between the ages of 16 and 24 were much more aware of how to report content across all categories than adults as a whole, but teens were slightly less aware than average.