It might be as simple as ‘liking’ a mean post on Facebook or spreading a rumour on Twitter. Sometimes it can make people self-harm or lead to them feeling suicidal.
If you’ve posted a video of someone else being hurt or shared someone else’s video it’s important that you delete it from your account to stop it being spread further.
If you’ve bullied someone else and you’re feeling worried about your behaviour, take a look at our bullying advice.
This could include pretending to be someone else and writing fake comments or blogs.
Bullying videos can be posted online on social media, live-streaming sites and photo sharing apps like Snapchat.