Tracking Protection allows you to take control of your privacy online. While Firefox has a Do Not Track feature that tells websites not to monitor your behavior, companies are not required to honor it. Firefox's Tracking Protection feature puts the control back in your hands by actively blocking domains and sites that are known to track users.
In the address bar, type about:config and press EnterReturn.
This will turn on Tracking Protection. If you later want to turn it back off, repeat the above steps to toggle the preference back to false.
Once Tracking Protection is activated, you will see a shield in your address bar whenever Firefox is blocking either tracking domains or mixed content.
You may choose to disable Tracking Protection for a particular site by clicking on the shield icon and selecting "Disable protection for this site." Once Tracking Protection is disabled for a site, you will see a shield with a red strike-through. You may choose to re-enable Tracking Protection for the site by clicking the shield icon again and selecting "Enable protection".
To see which resources are being blocked, you can open the web console and look for messages under the Security tab.