It should not come as a great shock that Facebook tracks your online behavior and partners with companies to target you with ads. But reigning in what Facebook knows is another matter.

Facebook, by partnering with retailers, can track your buying behavior both on and off Facebook. The goal is to help companies target you with ads as precisely as possible.

The moment you sign up for Facebook, it starts tracking who you interact with and what groups you join – a boon to advertisers. That’s the price you pay for using Facebook as a “free” service. Facebook explains its advertising policy and methods in various places on its site.

Facebook also owns WhatsApp and Instagram, so it is able to use that data as well. One of the reasons Facebook acquired Whatsapp was because of its heavy use by teenagers, an important advertising segment.

To limit how much of your personal data Facebook shares, a good place to start is the “Your Ad Preferences” page.

Here you’ll see under “Advertisers and Businesses,” companies who have run ads based your information.

Under “Your information,” you’ll see how ads are targeted based on relationship status, employer, job title, and education. Toggle these off if you don’t want this data to be used.

Further down the page, you’ll see “Ad settings.” Here, Facebook updated its controls to allow you to better control “Off-Facebook” activity. That is what gets tracked when you go to other sites not affiliated with Facebook.

Toggle this setting to “Not Allowed” for ads based on partner data.

“The setting used to control whether we show you ads based on your use of websites and apps off Facebook Company Products,” Facebook says.

“[But] now it also controls ads based on data we receive from partners about your offline activity.”

Also, toggle to “Not Allowed” for ads based on Facebook products “you see elsewhere.” And toggle to “No One” for social action ads.

Remember the goal is to reduce how much of your personal data Facebook can use. So, you’re not necessarily going to see fewer ads but fewer personal ads. Of course, you may prefer to see more ads pegged to your preferences so, if that’s the case, leave those settings alone.

In the end, the best way to stop Facebook from accessing your personal data is to stop using Facebook altogether. That might even improve your mood and in-person interaction with friends and family, among other things.