The site has been recording ABCe data for a year, but the group wanted to ensure the durability of its traffic growth before revealing the figure publicly. The site was relaunched in January.
The company also claims that UK page impressions have increased by 92% since December.
The May ABCe figure of 6.5 million worldwide unique users for Independent.co.uk puts the title behind market leader Mail Online, with 18.7 million unique users, Guardian.co.uk, Telegraph.co.uk, The Times and The Sun Online.
However, the May ABCe figure puts it ahead of Mirror Group Digital, which posted an ABCe of 4.8 million unique users in May.
Meanwhile, The Independent plans to bring its digital ad sales in-house to give it more control over operations.
AdLink, which has held The Independent account since 2001, was reappointed to the brief in early 2007.
The strategy to establish an in-house digital sales team for The Independent mirrors the set-up at other national newspaper sites, with Guardian.co.uk, The Sun Online, Times Online and Telegraph.co.uk all having their own dedicated digital sales teams.
United Kingdom
Independent web visitors shows huge increase
LONDON - Independent.co.uk, which posted its first ABCe figure of 6.5 million unique users in May, has revealed the number of unique UK users accessing the site has risen by 86% since December.