Online bullying among young people and children as young has seven has increased 88% in five years, the NSPCC has said.
Figures show Childline, the charity's helpline service, counselled 4,541 children in 2015/16, compared to 2,410 in 2011/12.
The levels of bullying - posted on social media profiles, blogs and online pictures - ranged from abusive words about appearance to death threats.
NSPCC chief executive Peter Wanless said: "Online bullying is one of the biggest child protection challenges of this generation. It is a problem intensified by the ever-increasing presence of the internet."
Almost half of young people aged 16-24 who had been bullied said listening to music made them feel stronger.
According to a new YouGov survey, more than half of Britons have been bullied in their lifetime.
Help for children and young adults, call Childline on 0800 1111. Adults concerned about a child, call 0800 800 5000.