The Firefox Maker, Mozilla has been a staunch advocate of the browser-side protection that block websites from following users online activities, which tracking is especially beneficial for advertisers who are targeting specific users, despite the fact that it invades their privacy.
While the issue of privacy has overtaken the Web service providers lately, and has often been a great bane for most internet users; Mozilla is harping on its new approach taking a leaf off Tor browser’s Anti-Fingerprinting Technique, with the introduction of Letterboxing in Firefox 67 which is scheduled for release in May.
The Letterboxing feature protects against the so-called window-size related fingerprinting, which is often employed in the profiling and tracking of Web users, whereby their personal information are collected from computing devices for identification.
Fingerprints is used by ad networks to identify individual users on the various devices been tracked, and it works even when browser cookies are turned off by the user; but with Letterboxing, Mozilla looks to add gray spaces to the browserside for the web page whenever the browser window is resized and removes all logs after exiting the resize operation.
What this means is that the browser window’s dimensions are masked by the adding of spaces to width and height in the multiple of 200px and 100px on resizing, with the gray spaces added at the top, bottom, left or right of the web page, and as advertising codes follow the window resize events to gather information.
Firefox 67 provides a generic dimension for such tracking to bring back the window to its actual size in milliseconds, thus delays the loading of the page content on the resized window long enough to trick the tracking codes to read the incorrect window dimensions.
This technique has since been in use by Tor Browser, from which Mozilla obviously borrowed the Letterboxing feature and it is currently available in Firefox Nightly.