National Children's Commissioner Megan Mitchell urged parents to be cautious when posting cute baby photos or sharing their children's latest achievements.

''It can put them at risk,'' she said. ''People can potentially find out what school they go to, or track where they move … because you have locational settings on.

''We have to be careful when we put images out there in the ether because we really don't know what is happening to them, we don't know who is going to access them and we don't know what they're going to do with them.''

She cited an example of an Australian man who posted a picture of his naked toddler in the bath on Facebook, thinking that it would only be seen by friends and family, only to discover that 3000 strangers had clicked on and ''liked'' the image.

NSW Privacy Commissioner Dr Elizabeth Coombs also warned parents against oversharing: ''The capability of technology requires us to be far more conscious of what information we make available and the possible consequences to others, including children.''

A US study found two-thirds of parents posted pictures of their children online. But a UNSW research project into children's wellbeing has questioned whether information parents post about their children violates their privacy and could potentially become a ''dirt file'' in decades to come.

Sydney mother Eugenie Pepper posts images of her children, Tommy, 6, and Chloe, 4, on YouTube, her personal Facebook page as well as the page of her children's wear business.

''My kids would be more offended if I didn't post photos of them,'' she said. ''I feel as if I am compiling these great memories and documenting their lives. They truly love it. I don't know how they will feel about it when they're older, but my gut is telling me that they're not going to care about it.''