According to the latest figures from the Audit Bureau of Circulation the site recorded a 21.17 per cent increase in total monthly browsers. Its daily average figure also rose by 21.4 per cent to 4,365,716 on average.
The MailOnline was also the first media owner to report iPhone app traffic as part of its ABC Certificate, following ABC's launch of app traffic metrics last month.
According to a press release the app, which launched six months ago, is recording more than 62,000 daily app unique browsers, requesting more than 3.8 million app page impressions.
All of the audited news sites in today's report from ABC show healthy increases on April, with the Independent's monthly online browsers rising by 18.47 per cent, the Telegraph's by 14.05 per cent and Mirror Group Digital's by 11.75 per cent.
The Guardian did not have a monthly increase figure available due to its decision to report the monthly statistics bi-monthly.
In a statement a Guardian spokesman said this was to focus on its daily traffic instead.
"We have for some time focused on reporting our daily average unique browsers measure, which the industry agrees is the most useful, robust and transparent way to monitor web traffic.
"To reflect this focus we will continue to audit and report our daily average unique browser figures on a monthly basis while reducing the frequency with which we audit monthly unique browsers on guardian.co.uk to once every other month."
Metro, which published its first ever traffic figures in January and so far also seems to only be reporting bi-monthly, recorded a monthly figure of 7,559,534 for May, an increase on the 6,478,889 reported in March.
Results for the Times and the Sun websites remain unreported, as requested by News International following the introduction of a paywall for the Times and Sunday Times sites last year.
Earlier this year ABC announced it had changed its policy to make it no longer mandatory for members to have their online traffic figures published at least once every 12 months.
The full figures for audited websites are listed below. The percentage in brackets indicates the month-on-month change compared with April's ABC multi platform report.
Average daily unique browsers: 4,365,716 (+21.4 per cent)
Monthly unique browsers: 77,250,993 (+21.17 per cent)
Average daily unique browsers: 2,827,677 (+17.46 per cent)
Monthly unique browsers: 51,383,937 (N/A)
Average daily unique browsers: 2,188,745 (+13.25 per cent)
Monthly unique browsers: 43,796,963 (+14.05 per cent)
Average daily unique browsers: 706,838 (+12 per cent)
Monthly unique browsers: 15,766,729 (+11.75 per cent)
Average daily unique browsers: 675,129 (+15.20 per cent)
Monthly unique browsers: 15,225,779 (+18.47 per cent)
Average daily unique browsers: 310,762 (N/A)
Monthly unique browsers: 7,559,534 (N/A)
No data available
No data available
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