The figure equates to one in four of the online population visiting a sports or gambling website as the 32 teams fought it out during the FIFA tournament.
This audience viewed over one million sports and gambling web-pages in total – averaging 71 pages per person
More than two thirds of these people were men with each averaging 48 minutes online, or three times as long as women, who surfed on average for only 16 minutes.
While 40% of the audience was aged 45-plus, it was the 25-44-year-old age group who averaged the longest time online at 47 minutes. This was almost twice as long as the under 25s at 25 minutes.
BBC Sport was the most popular site with 3.4m unique visitors giving it a 58% share of the total sports and gambling audience. the BBC was over three times as popular as its nearest rival, the official FIFA World Cup site.
Overall, gambling sites tended to be twice as sticky as sports sites. Bet365 was the stickiest of these site with its average visitor spending 2 hours 9 minutes online.
Alex Burmaster, European internet analyst at Nielsen//NetRatings, said: "The 2006 FIFA World Cup will go down as an extraordinary success online. The fact that over one in four people online in the UK, 6m million people, visited a sports or gambling website during the tournament - viewing almost half a billion web-pages - shows what an integral part online plays in the all-round experience of today's major sporting tournament."
He added: "The websites have provided a wonderful array of more interactive and engaging content than ever before. Whether this is text, photos, audio or video there has been something for everyone and, by the time the next World Cup comes around, the levels of interactive content online to maximise the experience of following the tournament could be absolutely mind-boggling."
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