Children now spend an average of 15 hours a week online and are becoming increasingly trusting of what they find, a study has revealed.
The amount of time eight to 15-year-olds spend on the internet has more than doubled over the last decade, Ofcom's report into media attitudes among children and parents found.
But these so-called digital natives - children who have grown up with the internet - often lack "online nous" to decide if what they see is true or impartial, the regulator concluded.
Almost one in 10 children who go online (8%) believe information from social media websites or apps is "all true" - doubling from 4% last year - and most 12 to 15-year-olds are unaware that "vloggers", or video bloggers, can be paid to endorse products.
Almost a fifth of online 12 to 15-year-olds (19%) believe information returned by a search engine such as Google or Bing must be true, but only a third (31%) are able to identify paid-for adverts.
The study found children are increasingly turning to YouTube for "true and accurate" information about what is going on in the world, with 8% of online youngsters naming the video sharing site as their preferred choice for this type of information - up from 3% last year.
But just half of 12 to 15-year-olds who watch YouTube (52%) are aware that advertising is the main source of funding on the site, and less than half (47%) are aware vloggers are often paid to favourably mention products or services.
Children aged 12 to 15 were split on whether being online helped them be themselves, with 34% agreeing and 35% disagreeing, while 31% were unsure.
The study did find that almost three quarters of older children (72%) believe most people behave differently when they are online, and more than two-thirds (67%) of older girls with a social media account said there were things they disliked about it compared with 52% of boys.
Almost a third (30%) were concerned about people spreading gossip or rumours and a quarter (23%) said people can be "nasty, mean or unkind to others".
Surprisingly, many children are also concerned about spending too much time online, the survey found.
Around one in 10 online children aged eight to 15 (9%) said they disliked spending too much time on the internet, and almost a third of 12 to 15-year-olds (31%) admitted they could sometimes spend too much time on social media in particular.
Almost all children - 97% - could recall advice they had been given about staying safe online, particularly from parents.
The large majority (84%) said they would tell their parents, another family member or a teacher if they saw something online they found worrying, nasty or offensive, but 6% of children say they would not tell anyone.