New figures show that over half of young people (52%) say someone has shared a photo or video of them online without asking their permission.
This is despite the fact that four in five youngsters say they know when and how they should ask.
Asking someone before posting something that features them is all to do with consent. Giving consent means giving permission for someone to do something.
People should ask for your consent before they post a photo or video of you online.
If you're posting a video or an image of somebody else, the rules say that you should have their permission to post it too.
But research carried out for Safer Internet Day suggests that this isn't always happening.
The figures also showed that sometimes it can be hard to say 'no' if someone does ask your permission.
One in three said that they had allowed someone to share a picture or video of them, even though they didn't really want them to.
It's also not just photos and videos that are shared without permission.
Sometimes private conversations can be made more public, without the people in that conversation necessarily knowing.
Over four in ten (44%) young people said someone has sent them a screenshot of a private conversation with someone else - even though fewer than one in ten think it's OK to share the contents of a private message.
If you're worried about something being shared when you don't want it to be, it's important that you talk to someone about it.
That might be speaking to the friend or family member who has posted, or talking to an adult that you trust.
Many young people enjoy sharing content online and engaging with content shared by others, and the research did show that there is a great number of positives to this.
Lots have been inspired to take positive action and share support for a campaign or social movement. Many more post in order to raise awareness of something that they think is unfair.
So we want to know what you think about sharing content online and permission.
Do you always ask your friend's or family's permission before posting content online that features them? Do your friends and family always ask your permission before they post photos or videos of you?
Do you think that enough is being done to make sure that people have given their consent before content of them is posted online?
UK Safer Internet Centre spoke to over 2,000 eight to 17-year-olds for Safer Internet Day