Google said it developed the tool "to provide website visitors with more choice about how their data is collected."
Analytics creates a cookie on a person's computer. Cookies are small data files used to record information about how a person interacts with a Web site.
Google's motivation in creating the add-on is likely defensive in case it comes under pressure from regulators over privacy concerns, said Daniel Brandt, president of the nonprofit Public Information Research group, and who runs the Google Watch Web site.
Analytics has come under scrutiny in Germany regarding whether the service violates data protection laws in the country.
"The reason is that there's no notification to the end user of the data that's getting collected by Web sites in Germany that are using Analytics," Brandt said.
Like all cookies, the cookie for Analytics is created automatically unless a user has installed an add-on to block it.
There are other tools for Firefox users that can block Analytics. Adblock Plus and NoScript can both be set to prevent Google Analytics from receiving any information from the browser, while OptimizeGoogle blocks the Google Analytics cookie in addition to modifying other aspects of Google's behavior, including blocking Google advertisements and modifying the user ID cookie Google assigns to users of its search engine so that they can surf anonymously.
Other cookie-management tools can also block the Google Analytics cookie, but won't stop Google Analytics from receiving more general information including the IP address of the Web user and the address of the page containing the Google Analytics tracking code.
Google Analytics collects the IP (Internet Protocol) addresses of Web site visitors but does not report the full address back to the site using Analytics. Google says that Web site operators can collect the IP addresses of visitors regardless of whether they use Analytics.
IP addresses can be used to identify a computer connected to the Internet and are regarded by some privacy advocates as personal information. While an IP address does not identify an individual user, it can be used by a service provider to identify a broadband subscriber.
The Analytics add-on does not stop Google from putting other cookies on a computer, such as its DoubleClick cookie, which tracks the Web pages a person visits and then serves advertisements related to that content.
The Analytics Opt-out add-on is compatible with Internet Explorer 7 and 8, Chrome version 4 and higher and Firefox version 3.5 and higher.
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