Firefox picks up advertiser-dodging tech from Tor

Firefox users will soon get yet another privacy feature to help them avoid snooping advertisers – and the measure comes straight from its cousin, the Tor browser.

The new privacy protection will help Firefox users avoid a long-used snooping technique called fingerprinting. Browser cookies are not the only way to track users as they visit different websites. Even with cookies turned off, advertisers can still identify you across multiple sites.

They do this by looking at other characteristics that your computer reveals when visiting a website such as the size of your browser window.

Many people resize browser windows by manually dragging their corners around. This creates random window sizes that few people will share. The chances are you’ll visit several websites in that window, which communicates its size to each one. Advertisers can use that data to track you across multiple sites.

To combat this, Firefox has borrowed a technique called letterboxing from Tor as part of a bigger, more structured program to transfer features between the browsers.