Stephen Shankland/CNET

Mozilla has released a Firefox tool called Facebook Container to stop the social network from seeing what you do online beyond Facebook's own site.

Facebook, like Google and other companies, can track you when you visit many websites, such as those that have a Facebook like button. It means Facebook gets more than just personal data it can use to target ads based on your profile.

It's also useful to companies like Cambridge Analytica, which is at the center of a sweeping privacy controversy stemming from its acquisition and use in political elections of data on more than 50 million Facebook users. That's because Facebook grants third-party apps and services some access to your data.

Facebook Container, an extension for Mozilla's Firefox web browser, essentially stops these trackers from working outside of the Facebook website, Mozilla said.

It's a new step in browsers becoming more assertive on behalf of everyone who uses them to protect privacy a little better. That's a notable change after the industry's Do Not Track effort failed to let us tell websites when we don't want to be tracked.

Among other assertions of browser power: Brave Software's Brave blocks ads and trackers; Google's Chrome has started blocking ads for sites that overuse them; Apple's Safari is cracking down on tracking; and Firefox has a new option to disable tracking and is experimenting with blocking in-page pop-ups that try to get us all to subscribe to newsletters, take surveys and redeem coupons.

The Firefox Container effort is an extension of Mozilla's work to isolate different browsing profiles to different compartments of the browser, something that makes it harder for website-tracking technology to piece together your interests, political leanings, spending patterns and other details.

"There's enormous value in tying this data to your social profile, and Facebook has a network of trackers on various websites. This code tracks you invisibly, and it is often impossible to determine when this data is being shared," said Nick Nguyen, Mozilla's vice president of Firefox, in a blog post.

"Facebook Container isolates your Facebook identity from the rest of your web activity. When you install it, you will continue to be able to use Facebook normally. Facebook can continue to deliver their service to you and send you advertising," Mozilla said. "The difference is that it will be much harder for Facebook to use your activity collected off Facebook to send you ads and other targeted messages."

When you first run the extension, it'll log you out of Facebook, delete any Facebook cookies, the text files browsers save and that websites use to keep tabs on you. The next time you load Facebook, Firefox will house it in a separate container labeled with the word "Facebook" in blue in the address bar.

For details on how the extension works, including a warning that Facebook Container can mess up websites where you use Facebook credentials to log in, check Mozilla's introduction to Facebook Container.

First published March 27, 6 a.m PT.

Update, 7:52 a.m. PT: Adds further details about the extension.

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