Facebook knows what millions of people do on their phones, even if they don’t actually use the social network, a new report claims.

The company is claimed to have been using data gathered from another firm for detailed insights on people’s app and website usage habits, such as which apps they use, how frequently they use them and even how long they use them for.

This information has also been used to shape Facebook’s product roadmap, and led to it buying WhatsApp and continuing to rip Snapchat’s Stories feature.

11 useful Facebook features you didn't know existed Show all 11 1 /11 11 useful Facebook features you didn't know existed 11 useful Facebook features you didn't know existed Clean up your News Feed Most of us are Facebook friends with some people we don’t actually care about, and there are several ways to keep their updates off your News Feed. The easiest option is to head to the column on the left and open News Feed Preferences. From here, you can prioritise friends, unfollow friends, refollow friends you unfollowed in the past and even block specific apps. 11 useful Facebook features you didn't know existed Change ad preferences You can view a list of everything Facebook thinks you’re into and tinker with your ad preferences. A lot more information is displayed on the desktop site than the app, so we’d recommend doing this on a computer. Just open Settings and select Advert Preferences. 11 useful Facebook features you didn't know existed Manage notifications You can get notifications about pretty much anything on Facebook these days, and that can be seriously irritating. Choose what you do and don’t want to be notified about by going into the Settings menu and selecting Notifications. You might be surprised by the number of sections you have to trawl through. 11 useful Facebook features you didn't know existed Save data Facebook automatically plays videos in your News Feed, and that’s a problem if you aren’t on a generous data plan. You can change this by going to Videos in the Settings menu and disabling autoplay. On the app, there’s feature in the left-hand column called Data Saver, which also does this, but reduces the size of pictures too. 11 useful Facebook features you didn't know existed Reorder your News feed You can choose to order the updates that appear in your News Feed by time or importance. Just hit the three buttons next to News Feed Preferences on the Facebook site and choose between Top Stories and Recent Stories. 11 useful Facebook features you didn't know existed Download your data Facebook lets you download all of the immense amounts of data it has on you, including the posts you’ve shared, your messages and photos, ads you’ve clicked on and even the IP addresses that are logged when you log in or out of the site. It’s a lot of information, which you’ll want to get your hands on if you decide to quit the social network. 11 useful Facebook features you didn't know existed Find nearby places Nearby Places is actually a really handy tool, which lets you quickly find and research things like restaurants, hotels, museums and nightlife hotspots around you. It lives in the left-hand column, and also shows useful information like customer ratings, prices and distance. 11 useful Facebook features you didn't know existed Find free Wi-Fi Similarly, Find Wi-Fi is ideal for when you’re bored, running low on data or lost. It shows you all the places in your vicinity that offer free Wi-Fi, so you can head over and either relax or get some work done. 11 useful Facebook features you didn't know existed Save things for later Facebook’s ideal for killing time, but every now and again you’ll stumble across something you’re interested in right as you need to put your phone away. Fortunately, you can save posts for later by hitting the arrow in the top-right corner and selecting the Save option. Everything you save goes straight to the Saved section in the left-hand column. 11 useful Facebook features you didn't know existed Control tags When people tag you in posts or pictures, they don’t have to automatically appear on your profile. You can switch on Facebook’s Review Tags feature by going to Settings and Timeline and Tagging. 11 useful Facebook features you didn't know existed Delete your account To permanently delete your Facebook account, you need to head to Facebook’s Delete Account page. The site can take up to 90 days to process account deletion requests, but once your account's gone, it’s gone. You can deactivate your account instead, by going to Security and Login in the Settings menu.

It's so precise that it allowed Facebook keep tabs on how many Snapchat posts users sent each day, the Wall Street Journal reports.

The setup essentially helps Facebook quickly work out which apps and websites it is competing with for screen time, and makes it a lot easier for the company to target and beat them.

We've asked Facebook for a comment, and will update this article if the company issues one.

It has been getting the data from Onavo Protect, a free VPN app that claims to help “keep you and your data safe when you go online”, which was created by a company Facebook bought in 2013.

The app is available on both Android and iOS, and has reportedly been downloaded by around 24 million users.

According to people familiar with the system, when anyone with Onavo Protect on their phone opens an app or visits a website, Onavo redirects the traffic to Facebook’s servers.

The details are logged in a database, and Facebook’s product team is then able to analyse it.

Apple and Google also have the ability to access similar information about their rivals' apps on Android and iOS, the Wall Street Journal adds, though it isn't clear if they've been using the data to improve their own products.

Though Onavo states that it “analyzes information about your mobile data and app use” and may share the data with “affiliates”, it’s likely that many Protect users failed to read the small print before downloading the app.

This setup reportedly allowed Facebook to figure out just how devastating an impact the rollout of Stories on Instagram had on Snapchat’s popularity and growth, long before Snapchat released any of the details itself.