Use this trick to see a map of everywhere Facebook knows you and your friends have been

We’ve already seen a nifty trick for viewing a map of everywhere Google knows you’ve been, but what about Facebook?

Well thanks to a clever Google Chrome extension discovered by The Next Web, you can now explore your own map of every location Facebook knows you and your friends have been — using only the location data that is often attached to your conversations over Facebook Messenger.

The map hack is so accurate that it’s even able to show you where you and your friends have been when messaging each other to within a meter.

Created by student developer and future Facebook intern Aran Khanna, the hack is called “Marauders Map” after the magical map that revealed the location of Hogwarts students in “Harry Potter.” And don’t worry, while a bit creepy, the hack and Google Chrome extension are perfectly legal, with the Chrome extension simply populating a map with locations already tied to your Facebook Messages.

Of course, the Marauders Map only reveals the locations of conversations where both you and your friends both had location sharing enabled, but many people forget that the setting is turned on by default in the Facebook Messenger app, so you might have shared more locations than you realised.

How to see your own Marauders Map

First, you’ll need to be using Google Chrome as your web browser and head on over to the Chrome Web Store and download the free Marauders Map extension.

Once you’ve installed the Chrome extension and authorised it to pull in data from Facebook, you can head on over to https://www.facebook.com/messages/ to see a list of your past Messenger conversations. Next, simply makes sure your browser window is fully expanded (don’t shrink the window down to a smaller size), and you should notice a blue box with a map pop up in the lower left corner of your screen.

You can minimise the map by clicking on the blue toolbar, and bring it back up by clicking on the words “Marauders Map.” This is the map you’ll see populated with tiny chat bubbles representing you and your friends as you sift through your past conversations.

To get started, you’ll need to click on a conversation within Messenger and scroll upwards to the beginning of the messaging thread. This ensures all possible data points are added to the map, and you should notice the map beginning to populate as you go. If you don’t see anything, chances are either you or your friend in that particular conversation had location sharing turned off.

You can click on other conversations to load more data points, and feel free to zoom in and out to get a closer look. It should look something like this.

Clicking on any of the chat bubbles will bring up a detailed spiderweb of everywhere you or your friends have been throughout your messaging history, with the bubble representing the most recent location.

In a blog post on Medium, Khanna writes that “by gathering a couple weeks’ worth of chat data on the map and looking at the location clusters you can even figure out [my friend’s] weekly schedule. With this you can predict exactly which building he would be in at a given time.”

It’s no surprise that Khanna now chooses to disable location sharing when using Facebook Messenger, and keep in mind that’s always an option.

If you want to make sure you never share your location inside Messenger, simply navigate to the Settings cog inside your iOS and Android Facebook Messenger app and uncheck the box marked “Location.” You can also go to your iPhone’s Settings app, tap Privacy > Location Services > Messenger and select “Never” to revoke Facebook Messenger’s location sharing privileges.

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