Mozilla has been working on a privacy feature called Tracking Protection for some time now. The feature is currently only available in Nightly versions of the desktop version of the web browser and there only after activation. The feature landed in Firefox for Android too but has not found its way to the stable version of the mobile browser yet as well.
What it does, at least in its current form, is to use data provided by Disconnect to block certain web trackers from being executed on websites that you visit.
This works similar to other blocking-type of extensions but with the difference that you have no control over the list, at least not right now.
That does not mean that you cannot allow contents to run anyway in Firefox. A shield icon in Firefox's address bar indicates whether trackers are blocked or not on the active web page.
A click on the icon displays options to disable the protection for the site you are own which Firefox then indicates by a different shield icon.
Up until now, Tracking Protection worked only in regular browsing mode but not in private browsing mode. Considering that private browsing has been designed to block data from being recorded locally, it makes sense to add remote blocking to it as well to limit exposure on the Internet.
The mode is not enabled by default just like the regular tracking protection modes.
- Type about:config in Firefox's address bar and hit the enter key.
- Confirm you will be careful if the message comes up.
- Search for privacy.trackingprotection.pbmode.enabled and double-click on its name afterwards to set its value to true.
- This enables the feature from that moment on.
To turn it off again, repeat the first three steps above and make sure that the parameter is set to false in the end.
Side tip: To enable Tracking Protection for all non-private browsing pages you visit in Firefox, set browser.polaris.enabled to true which does that and adds the new preference to Firefox's privacy menu in the options where you can turn it off or on as you see fit. You could set privacy.trackingprotection.enabled to true alternatively but that won't add the menu option to the privacy menu.
It makes sense to add tracking protection to the private browsing mode as it improves your privacy further when enabled. While that is without doubt no 100% protection against leaks, it is a next step to improve the mode for all users of the browser.
Considering that Tracking Protection is still only available in Nightly versions of Firefox, it is fair to say that Stable users of the browser will have to wait at least three releases before the feature lands in their version of the browser. (via Sören)