Apple is the latest in a series of Web browser makers to add a new privacy feature that keeps online advertising networks and other tracking tools from monitoring user activity.

According to The Wall Street Journal, the latest developer preview of Apple's Mac OS X 10.7, codenamed "Lion," sports a version of Safari with a do-not-track feature built in.

Do-not-track is technology that allows users to opt out of being tracked by third parties in a similar fashion to the do-not-call lists for telephones. The movement accelerated following a report released last December by The Federal Trade Commission, urging technology makers to implement the technology into their products to protect consumer privacy. While legislation to put some teeth on enforcing it has stalled, browser makers like Mozilla and Microsoft have released do-not-track tools in the latest versions of their browsers.

Meanwhile, Google, which makes the Chrome browser, released a do-not-track tool in January that users are required to download and install as an add-on.

Lion is currently on its second developer preview and requires that developers and users who are testing the software stay tight-lipped under a non-disclosure agreement. Apple is expected to unveil a price, release date, and more details about the software at its Worldwide Developers Conference in early June.

Apple did not immediately respond to a request for comment on whether the do-not-track feature would make it to the current Mac OS X, or if it would be available to Safari users on Microsoft's Windows platform.