Firefox to Add Tor's Anti-Fingerprinting Technique

The third most popular web browser Mozilla Firefox is known for its privacy-oriented features. It’s free and claims to be 44% faster than the other popular browsers. With an aim to keep the internet open and accessible to all, Firefox comes with some useful features like private browsing that blocks online trackers, faster page loading, etc.

Mozilla keeps updating its browser to cope with the latest user tracking methods. This time Mozilla is planning to add Tor’s Anti-Fingerprinting technique in Firefox 67. The technique is dubbed as ‘Letterboxing’ and the update is scheduled to be released in May 2018.

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What is Browser Fingerprinting?

If you don’t know, Browser fingerprinting is a precise method of identifying unique browsers and tracking the online activity of users. These fingerprints can be used by several external agencies like advertisement networks to partially or fully identify users and their devices. The most important thing about Browser fingerprinting is that it works even after cookies are turned off.

The technique ‘Letterboxing’ protects the users against window-sized fingerprints. It will basically add ‘grey spaces’ to the side of the web pages whenever a user resizes the browser window and removes after the user return back to the original size.

The new technique will mask the actual dimensions of the window by adding spaces in multiples of 200px and 100px while resizing. it will add the grey spaces at the top, bottom, right, or left of the web page. As the advertisement display codes monitor the window resize event and makes the process slow, Firefox 67 will provide some general dimension to them, and bring back the window to its actual size in a few milliseconds.

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These few milliseconds are basically required to trick the scripts and habit trackers to read the generic dimensions. As the delay time is not so large, user experience won’t be affected.

How to Enable Anti-Fingerprinting Feature?

The Anti-fingerprinting Letterboxing feature is not enabled by default. To enable, you will have to visit “about: config page”, look for “privacy.resistFingerprinting” using the search box and finally set the anti-fingerprinting feature to “true.”

If you are thinking that Letterboxing is some new technique, you are wrong. It was formerly developed for Tor browser in 2015. Though the concept is still the same but difference lies in its implementation. “In Tor browser, it kept the entire browser window at preset dimensions, while the Mozilla version uses grey spaces to let the browser window show at any size, but keep the page content at preset dimensions.” Mozilla spokesperson told ZDNet.

Letterboxing is currently available for Firefox Nightly users and will be expected to roll out with Firefox 67 in May 2018.