Children are stumbling across foul language, violence and sexual content on YouTube, but keeping them safe online is increasingly falling to parents.
A SpongeBob SquarePants video dubbed with explicit hip-hop lyrics. A violent trailer for an R-rated horror film that played at the beginning of a Fireman Sam video. An episode of Disney series Doc McStuffins with subtitles riddled with expletives.
These are just a few examples of inappropriate content Kiwi kids might have stumbled across in the past few months when watching child-friendly clips on the world's most popular video-streaming site, Google-owned YouTube.
For many parents, YouTube is a godsend, offering instant entertainment on long car rides, in doctors' waiting rooms, or just keeping the kids entertained for the half-hour before dinner.
It can also be a goldmine of information, whether you want a clip to help a child learn a musical instrument, teach them spelling, maths or colours, or be inspired by elaborate science experiments.
But with the good comes the bad - brutal violence, sexual content, in-depth examinations of all manner of stomach-turning physical ailments - and the just plain weird, such as a how-to video of DIY prostate exams.
That has left parents asking how anyone can control what kids access on a platform that has 300 hours of video uploaded every minute.
It is a concern that is being raised around the world and one YouTube is tackling with only mixed success. Earlier this year, it launched its child-friendly-content YouTube Kids app.
It is not available in New Zealand yet and has received a lukewarm welcome in the US.
Consumer groups there are worried inappropriate content is slipping through the app's checks and parents have complained about encountering pornographic cartoons, graphic violence and alcohol advertising.
YouTube says it is committed to making the app available internationally but a spokesman could not say whether it had a date for a New Zealand release.
Google also offers YouTube Safety Mode, which filters out clips labelled age-restricted or flagged as having "mature" content.
But this relies on other users to correctly identify the content and it has to be enabled on every browser that kids are using. YouTube says it should not be expected to be 100 per cent reliable.
Auckland University senior lecturer in psychology Annette Henderson says it is impossible for the site to keep tabs on what its users post. It is estimated four billion videos are watched every day.
"Content is being uploaded so rapidly they can't keep up," Henderson says. "Parents cannot put faith in their monitoring. We want to be able to take a multi-pronged approach to this, where the companies do what they can and parents do what we can to teach children to be aware of what they are looking at and why we might be concerned about it."
She says worries about YouTube are common. "It's not a lot different from what we experienced many decades ago when parents might have had books they did not want their children to read, but people think it is different because it is right at their fingertips and technology is integrated so much into their learning."
Henderson says the best bet to manage YouTube content is to keep the lines of communication open and regularly talk about what kids are doing online.
Parents should relate things back to situations children will encounter in their day-to-day lives, she suggests. "If it's kids fighting in a playground you can say it's not something you want to encourage people to keep doing.
"You can identify uncomfortable situations across a number of domains and generally engage in conversation about what they think and what they might want to look at instead."
Rochelle Gribble, editor of parenting website Kiwi Families, says monitoring what kids access is becoming more difficult as children start to use a number of different devices, such as an iPad or smartphone alongside their PC.
"The advice to keep the PC in the living space is no longer relevant."
Gribble says a lot of kids are led astray by the suggested links at the end of each YouTube clip. They can end up viewing content a world away from what they started off looking at, or from what parents think they are watching.
Parents can subscribe to YouTube channels and ask kids not to stray from them, or make a playlist of clips they were happy with, she says.
But the best way to tackle it is for parents to get involved with what their kids were watching, Gribble says. "No one wants to watch Dora for 10 hours but you need to be paying attention, checking in, not just handing them the iPad.
"All this stuff is part of digital literacy, which you should be already dealing with. They will be accessing the internet and there is stuff you only have limited control over."
Kids should be told to talk about anything they encountered that made them uncomfortable, she says. "Make everyone very open about these things." They need not to be "scared, secretive or want to hide".
If the videos are not enough to worry about, there are advertisements, too. Some bloggers stealthily include inappropriate advertising messages in their clips and there may be unwanted advertisements showing before videos.
In most cases, advertisements on YouTube videos are determined automatically by Google's AdSense system.
That can mean ads for beer might play before cartoons, or violent trailers for horror films.
Britain has a campaign asking for "vloggers" to be subject to the same advertising standards that apply to children's television.
Martin Cocker, of Netsafe, says some children can't tell what is an advertisement in YouTube clips.
Younger people have lower levels of media literacy and are more likely to misconstrue an advertisement as factual. "That's one concern.
"Another is advertising inappropriate things to young kids. You might get dating sites or adult-content advertisements."
Wellington mum Pip Rudhall says her 15-year-old daughter is hooked on beauty bloggers, although she is becoming more aware of the commercial nature behind some posts. "They're not all sponsored posts but a lot are. Through school, she learns about marketing and the tips and tricks they do to make people buy things."
But does this mean YouTube should be blacklisted and kids kept away until they turn 18? Definitely not, says Henderson. YouTube is a valid learning tool.
"It can be a positive experience if the content is right."
If parents are willing to sit with their kids and watch clips with them, it can be educational.
"A lot of the time these sites and iPads are used as a babysitting element: 'I need to do something so I'll give this to my child to do to keep them busy.'
"That's when it's challenging. You're not there to keep track of what is played with and watched. Doing that removes the valuable social interaction experience that can happen.
"If parents are sitting with the child watching these things and are actively engaged it can be a bonding moment and also learning. 'What did you just watch, why did you find that interesting?'
"Encourage your child to be mindful of what they're doing, and asking the questions."
She says parents need to identify ways to harness tools such as YouTube to engage with their child.
"Watching something that has no learning value is different from watching something with a lesson. Lots of children-directed shows have a learning lesson that kids might not get, so if parents can sit and talk with them it's a learning opportunity."
Cocker agrees. "YouTube is used by schools and educational institutions to deliver valuable content.
"There's some really good stuff there but lots of rubbish, too. I wouldn't say ban them or block them from your house.
"But it's a good idea to understand pretty well as a parent so you can discuss the challenges kids encounter."
Not a kid-friendly place
Alesha Stewart was listening to her son watching SpongeBob SquarePants videos when she realised something was not right.
Instead of the usual upbeat chirpy banter between the characters, "it was: 'bitches and hos'."
Someone had taken the original child-appropriate cartoon and dubbed an adults-only soundtrack over it. Michael, then 5, did not realise anything was wrong but Stewart quickly closed it down.
"I was on him so fast. But it's the moving pictures that attract them."
She soon realised there are plenty of inappropriate SpongeBob videos, but little way for Michael to know which to pick.
He searches for a cartoon by its name and related videos pop up. He picks one and then more suggestions keep on coming. "The more he clicks, the further away he gets from the original thing."
She will consider further safety measures as he gets older.
"I have an apps lock on the tablet, where he has to put in a code number to access parts of it, so he can't get on YouTube without me knowing.
"But once he is on he can roam and end up anywhere. That's where I have to keep and eye or ear out.
"It's probably worth looking into what controls are available because it's not a kid-friendly place, it's where dickheads make inappropriate cartoons that aren't controlled by YouTube."
She said even music videos could cause her to raise an eyebrow. "Some things can be borderline, with him loving Katy Perry and somehow he likes peacocks, when he realised she had a song called Peacock he was thrilled.
"Me, not so much. The lyrics are a bit adult for a child. He then memorises them and sings."
She tried to supervise her son as much as possible. "But when he is looking at cartoons, you expect it's just cartoons."
Forrest Hill mum Vanessa Cairns had a nasty surprise this year when her sons, watching videos about popular game Minecraft on YouTube, were propositioned by a stranger.
Morgan, 11, and Cameron, 7, were with friends when they started to receive unwelcome messages.
"It was someone linking in from another country, asking some seedy questions, along the lines of wanting to hook up for sex. I heard one of the boys say, 'That's really inappropriate'."
Cairns investigated and the boys quickly exited to get away from the messages. Cairns had already asked the boys to specifically search for "no-swearing" Minecraft videos to avoid some of the more expletive-riddled how-to clips.
"Good on him for saying something, it probably took him by surprise. I think it depends on the child [how they react], some might have logged off and not said anything but I think it was a shock even to him."
She was worried about the sort of content they might be exposed to as they got older and was considering using parental control software such as Net Nanny to monitor their internet use.
"The boys are pretty innocent at the moment and pretty open with us."