How to Enable Letterboxing Anti-Fingerprinting Feature in Firefox 67

[The AchieVer]

How to Enable Letterboxing Anti-Fingerprinting Feature in Firefox 67 

Mozilla has recently updated Firefox with new privacy controls that make it much harder for advertisers to track users, and the company continues work in this regard with further improvements planned for the next browser updates.

In Firefox 67, for example, Mozilla will debut a new anti-fingerprinting feature called letterboxing and which was originally implemented in TOR browser.

The purpose of letterboxing is to block advertisers from creating user profiles based on collected information, like the window size. Basically, what the letterboxing method does is add a gray space around the content in the active browser window so that the tracker wouldn’t read the dimensions correctly.

In a post on Bugzilla, a Mozilla engineer explains that the Firefox implementation would be based on the same approach as in Tor Browser.

“In our prototype, when a user drags the corner of a window, the viewport "snaps" to the largest contained multiple of 200 x 100, leaving a temporary margin of empty gray space in the window chrome. Then, when the user stops resizing (the "resizeend" event), the margin of the window "shrinks" to nothing so that the outer chrome tightly encloses the viewport again,” the post reads.

“When the user maximizes the window, the largest possible viewport is used, again a multiple of 200 x 100. Empty gray margins in the chrome part of the window cover the rest of the screen. Similarly, in fullscreen, the viewport is again given dimensions a multiple of 200 x 100, and the chrome areas around it are set to black.”

This feature is projected to become available for users with the release of Firefox 67 in May, but Mozilla is already testing it with the help of the Nightly version of Firefox. This means that users can give it a try already if they install this experimental version of the browser.

This tutorial is based on Firefox Nightly 67.0a1 (2019-03-06), so you need to be running at least this version to be able to try out this early letterboxing implementation.
 

 

 

First and foremost, launch Firefox Nightly, and in the address bar type the following command:

about:config

Next, in the search box, you need to search for a dedicated flag that is called:

privacy.resistFingerprinting

By default, this flag is set to false, which means that it’s disabled and the letterboxing doesn’t run. So what you have to do is to click the Toggle button and set its value to true.

At this point, the letterboxing feature should be up and running in your Firefox browser, and resizing the browser window shouldn’t let any information get through.

As per GHacks, there are several websites that let you test if letterboxing is working correctly in your browser, and one of them is Browserleaks. Just open this page in Firefox Nightly with the feature enabled and disabled and check the screen resolution and viewport fields to see if the letterboxing is active.

While this is a feature that many are looking forward to, enabling anti-fingerprinting features in the browser could break down certain services, including captchas, whose verification often fails with no workaround until the protection system is disabled.

Mozilla Firefox 67 is projected to launch on May 14, 2019, so the parent company still has enough time to refine its performance should it want to enable letterboxing by default in the browser. For the time being, however, this feature continues to be available as an experiment in the Nightly build of Firefox, so anyone can give it a try and see how everything works.

 

 

 

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