British web users are spending 65% more time online than three years ago, according to research of net habits.
The average surfer spends 22 hours and 15 minutes on the net each month, according to the UK Online Measurement company (UKOM).
The lion's share of that time is spent on social networks or blogs, which accounts for nearly a quarter of users' time online.
Instant messaging (IM) has been one of the victims of social network growth.
Three years ago 14% of online time was spent using IM but that has fallen to just 5%.
But e-mail, also predicted to suffer as more people used Facebook and its rivals, is still healthy and accounts for 7.2% of time compared to 6.5% of time three years ago.
Networking, communication and playing games remain the most popular online activities.
"These are the pillars on which the internet are built," said Alex Burmaster, a spokesman for UKOM.
The use of online classified adverts and auctions is creeping up the usage table, accounting for 4.7% of time.
Online news has also seen strong growth with 2.8% of online time spent browsing such sites compared to just 1.5% three years ago.
People spend more time on news sites than they do on adult content, the survey shows.
"It is a bit of a digital myth that everyone online visits adult sites," said Mr Burmaster.
"We divide the internet into 85 different sections so the fact that adult content is in the top 10 shows it is still one of the most heavily used sectors," he added.
He puts the rise of social networking down to its organic nature.
"It is like an organism, feeding off itself and getting bigger. People are plugging more and more of their lives into it," he said.