• Don't forget that sharing a post to a social networking site such as Twitter, means it's available for anyone to see.
The rise of mobile devices means keeping children safe online has become more difficult, experts say.
They were speaking at the launch of Instagram's Parents Guide in Wellington today.
The photographic and video sharing application, owned by Facebook, is growing in popularity, with most users using the app on mobile devices, Instagram global head of policy Nicky Jackson Colaco said.
"The days where you could see what teenagers were up to on a family computer in the centre of the house - those days are over."
It was important for parents to teach their children that respecting others in how media was shared, tagged and commented on, reduced risk.
They should also ensure their children were not posting provocative pictures or interacting inappropriately with people they did not know.
Mobile devices had an average of 29 apps installed on them, meaning parents needed to understand dozens of apps to know what their children were looking at, Ms Jackson Colaco said.
"Almost 70 per cent of 18 to 24-year-olds used social networking sites everyday."
Instagram had a number of safety features that parents and their children should know about, she said.
Photos or comments of photos could be reported to the Instagram team.
Images indicating a suicide threat or self-harm would be reviewed within 24 hours and appropriate authorities would be contacted, Ms Jackson Colaco said.
Many teenagers would automatically turn on the privacy settings on Instagram so not just anybody, including their parents, would see their content.
"They're not necessarily doing anything bad, they just like their privacy."
Users could also block others from their content, which was a good way to stop trolls, she said.
Teachers also had a role in teaching students how to stay safe.
"Teachers have a lot on their plates...but our hope is they will familiarise themselves with [popular apps]."
Lee Chisholm from NetSafe said all users should learn about the tools to keep users safe, such as reporting or blocking other users.
"Often they learn about these things too late."
The NetSafe contact centre received 8000 to 9000 queries per year, with about 15 per cent around social media concerns, she said.
By the numbers:
• 2.4 million New Zealanders use Facebook, with numbers growing for Instagram;
• 74 per cent of mobile traffic in New Zealand comes from a smartphone; and
• The minimum age for starting an Instagram account is 13.
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