The story
StatCounter (Jan 2009 to October 2019)
StatCounter statistics are directly derived from hits (not unique visitors) from 3 million sites using StatCounter totaling more than 15 billion hits per month. No weightings are used.
W3Counter (May 2007 to December 2022)
This site counts the last 15,000 page views from each of approximately 80,000 websites.
This limits the influence of sites with more than 15,000 monthly visitors on the usage statistics.
W3Counter is not affiliated with the World Wide Web Consortium (W3C).
Net Applications (May 2016 to November 2019)
Net Applications bases its usage share on statistics from 40,000 websites having around 160 million unique visitors per month. The mean site has 1300 unique visitors per day.
Wikimedia (April 2009 to March 2015)
Wikimedia traffic analysis reports are based on server logs of about 4 billion page requests per month, based on the user agent information that accompanied the requests. These server logs cover requests to all the Wikimedia Foundation projects, including Wikipedia, Wikimedia Commons, Wiktionary, Wikibooks, Wikiquote, Wikisource, Wikinews, Wikiversity and others.
Note: Wikimedia has recently had a large percentage of unrecognised browsers, previously counted as Firefox, that are now assumed to be Internet Explorer 11 fixed in the February 2014 and later numbers. And February 2014 numbers include mobile for Internet Explorer and Firefox (not included in Android). Chrome did not include the mobile numbers at that time while Android does since there was an "Android browser" that was the default browser at that time.
StatOwl.com (September 2008 to November 2012)
92% of sites monitored by StatOwl serve predominantly United States market.
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AT Internet Institute (Europe, July 2007 to June 2010)
AT Internet Institute was formerly known as XiTi.
Method: Only counts visits to local sites in 23 European countries and then averages the percentages for those 23 European countries independent of population size.
TheCounter.com (2000 to 2009)
TheCounter.com, a defunct web counter service, identified sixteen versions of six browsers (Internet Explorer, Firefox, Safari, Opera, Netscape, and Konqueror). Other browsers are categorised as either "Netscape compatible" (including Google Chrome, which may also be categorized as "Safari" because of its "Webkit" subtag) or "unknown". Internet Explorer 8 is identified as Internet Explorer 7. Monthly data includes all hits from 2008-02-01 until the end of the month concerned. More than the exact browser type, this data identifies the underlying rendering engine used by various browsers, and the table below aggregates them in the same column.
From Wikipedia’s article on Net Applications, shared under CC BY-SA 4.0.3