A new Facebook privacy policy allows the site to track your activity even after you’ve left it — and all users have automatically signed up to it.

The change enables it to gather data from activity across the internet, as well as the normal data it gathers on information you and your friends have added to the site. It also allows the site to pass on that information with its other branches, including Instagram.

Facebook does not share data with WhatsApp or vice versa, the company said.

The company said in November that the change would come into effect, when it mentioned that it would be implemented on January 30. Facebook says that it showed notifications to users, and sent them emails, informing them that the change was coming into effect.

It also ran a seven day comment period, allowing users to discuss the change.

Facebook privacy settings you should know about Show all 6 1 /6 Facebook privacy settings you should know about Facebook privacy settings you should know about Change who sees your posts. Anything you post on Facebook - from a status update to a photo - can be given its own privacy setting. 'Public' means that the information can be found via Google, or you can create custom groups of friends (http://ind.pn/1bVJJ2H) to share info with. Remember: whatever setting you last choose will become default until you change it again. Facebook privacy settings you should know about Check what your friends are sharing about you. Sometimes it's not you, but your friends that give information away. Follow this link to see the information that your friends might be sharing with third party apps - http://ind.pn/1bVVar6. Click the 'edit' option to the right of 'Apps other use' and un-tick every category of info you don't want to share. There's also an option above labelled 'Apps you use' that lets you select which apps can use your Facebook data elsewhere on the web. Don't trust them? Click the little cross on the right. Facebook privacy settings you should know about Hide old posts. If you're keen to make your Facebook past more private, limiting who can see your old posts should be your first step. Follow this link - http://ind.pn/1bVK7hv - and click 'Limit The Audience for Old Posts on Your Timeline'. You can make all of these old photos and stats updates vieweable to the public, friends only, or just yourself. From this page you can also change who can send you messages and friend requests. Facebook privacy settings you should know about Create friend lists. Since September 2011 Facebook has let you create different 'lists' of friends in order to let you separate what your close buddies and your work colleagues see. Facebook can give you a head start by suggesting lists based on who you went to school with and where people live - and you can even choose to browse a News Feed populated only by a certain list. Follow the link below for a full guide: http://ind.pn/1bVPu0d Facebook privacy settings you should know about Limit adverts. Pages you like will sometimes be used by Facebook to endorse a product to your friends. If you don't wnat these to show up head to this page - http://ind.pn/1j6Mc2b - select "Pair my social actions with adverts for no one" and click Save Changes. Facebook privacy settings you should know about Check your profile. If you're still worried about which of your photos or posts are visible to people you can check what the public (or any specific individual) sees when they click on your profile. View your profile by clicking on your namem then click the cog in the bottom right hand corner of your cover photo, then select 'View as...'

Facebook says that the data used will help personalise advertising and stop users being shown information that they don’t want.

Advertising is key to Facebook’s revenues, and drove the surging profits that the company reported last week.

Users can opt out of some parts of the new policy by customising privacy settings. The site has a special settings page for ads, where users can opt out of advertising that is shown on third party sites or is selected by comparing you with your friends. Adjustments can also be made on mobile devices.