Nearly a third of teenage girls have been sexually harassed online by children their own age, a study from charity Childnet suggests.
Some 31% of girls aged 13-17 have been targeted with unwanted sexual attention, compared with 11% of boys.
One in 10 of the 1,559 teens interviewed reported receiving threats of sexual violence, including rape.
The government is currently preparing new guidance on how schools deal with sexual harassment.
Other findings of the report are:
- 26% of teenagers have been a victim of online rumours about their sexual behaviour
- 12% of teenagers claimed they have been pressured by partners to share naked images
- 33% of girls and 14% of boys report sexual comments posted on images they share online
- 23% know of someone secretly taking sexual images of another person and sharing them online
- Half report seeing revenge porn - sexual images taken and shared without consent - circulating online
- Almost a third (31%) have seen people their own age creating fake profiles in order to share sexual images, comments or messages
- 47% have witnessed "doxing" where young people share personal details of someone who is seen as "easy"
The report found that sexual harassment occurred across a range of platforms, from messaging apps such as WhatsApp to social media sites such as Snapchat.
Will Gardner, chief executive of Childnet said: "Digital technology plays a central role in young people's lives but it has opened the door for a range of new forms of sexual harassment, making societal discussions about these issues more pertinent than ever.
"It is evidently something that as a society we can no longer ignore. This report underlines how essential it is that we all work together to ensure that online sexual harassment is not an inevitable part of growing up."
The charity is working to develop educational resources to equip schools to prevent and respond to online sexual harassments among pupils.
Snapchat has made it easier for users to block and report unwanted messages by holding down on the account name and tapping to report.
It claims to respond to reports within 24 hours of being reported and it has a safety centre with guidance.
Facebook - which owns WhatsApp - has previously claimed that it takes the issue seriously and is currently funding training for one young person in every UK secondary school to support children who experience cyberbullying.