Most major websites track their visitors' behavior and then sell or provide that information to other companies. This information can be used to show ads, products or services specifically targeted to you. Firefox has a Do Not Track feature that lets you tell every website you visit, their advertisers, and content providers that you don't want your browsing behavior tracked.
Honoring this setting is voluntary — individual websites are not required to respect it. Websites that do honor this setting should automatically stop tracking your behavior without any further action from you. Turning on this feature will not affect your ability to log in to websites nor cause Firefox to forget your private information, such as the contents of shopping carts, location information or login information.
Note: You may see less relevant advertising on websites if you have the Do Not Track option activated.
How do I turn the Do-not-track feature on?
The Do-not-track feature is turned off by default. To turn it on:
On the Privacy screen, put a check mark next to Do not track.
Other tracking options
There are two other tracking options:
Tell sites that I want to be tracked: Choosing this option will tell websites that you want to be tracked by advertisers and other third-parties. You should be aware that many companies build a profile of sites you visit. Checking this option means that you are okay with that.
Do not tell sites anything about my tracking preferences: This is the default setting. Choosing this option will not tell websites anything about your preferences. You should note that this does not mean that you will not be tracked. In fact it's effectively the same as the previous option, and you are likely going to be tracked.
Tracking Protection: If you have Tracking Protection turned on, Firefox will tell websites not to track you, regardless of your Do Not Track setting.