Safari in Mac OS X 10.7 will come with a built-in 'Do Not Track' feature, according to reports.

The Wall Street Journal said it had noted a number of conversations about the feature, which has been included in the latest test build of Lion, on Apple's Discussion forums.

Other browsers such as Firefox 4 and Microsoft's Internet Explorer 9 both have similar options, allowing users to prevent details of their online activities being monitored by marketing firms.

However, rather than actually preventing the monitoring of the data, the 'Do Not Track' systems simply send out messages to websites and online advertising networks that a particular user has specified that they don't wish to have their activities tracked, and rely entirely on the sites and networks in question honouring that request.

Google, meanwhile, offers an add-on for Chrome called Keep My Opt-Outs that gives users the option to permanently opt out of ad tracking systems.

Mac OS X 10.7 Lion is due to launch at some stage this summer.