Almost one in 10 desktop Firefox users have enabled 'do not track' on the browser, with a much higher proportion of Firefox for Android users doing the same.

Do Not Track (DNT) is an emerging standard that lets people tell websites that they do not want to be tracked with cookies as they surf. The way in which it is implemented is the subject of furious debate , with privacy advocates saying it should do what it says on the tin, and advertisers claiming that marketing tactics should never be blocked .

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In a blog post on Friday, Mozilla Firefox engineering chief Johnathan Nightingale said eight percent of desktop Firefox users have enabled DNT, while 19 percent of those using the browser on an Android device have done the same.

According to Nightingale, this proves that "there is a real user appetite for choice on issues of web privacy".

The statistics came as part of a round-up of Mozilla's activities this year. Other highlights include the passing of the three-billion mark for Firefox add-ons, and the shipment of the popular browser in 89 languages.

Firefox is the third-most-used browser in the world, behind Chrome in first place and Internet Explorer in second.

Mozilla is in the process of building a Firefox OS for mobile devices . According to Nightingale, work on the operating system has already resulted in the release of 30 new web APIs "to bring the power of mobile apps to the open web".

"For Firefox OS, 2013 will be the year when the world can see and hold and try a real device powered only by the power of the web and, for many, it will be the first smartphone they've ever been able to afford," Nightingale wrote.