Firefox 4 and higher has a feature to inform websites not to track your usage across the web. You can turn this feature on by selecting "Tell web sites I do not want to be tracked" in the Firefox options window. This article describes what tracking is and how this feature works.

What is tracking?

Tracking is a general term encompassing a variety of techniques that websites, advertisers and other entities use to learn about the websites you visit and what you do on them. In particular, tracking is often done by advertising networks who present ads on many different sites. By logging the sites you visit and what actions you take on them, these ad companies are able to build a highly specific profile based your browsing activities including shopping preferences, demographic information, likes and dislikes. This profile allows them to present advertising targeted to you specifically. They can also combine their knowledge of you with their understanding of other people to build algorithms that allow more effective marketing of products and services to users like you.

How does the Do-not-track feature work?

When you turn on the Do not track feature, Firefox tells every website you visit (as well as advertisers and resources used by those sites) that you do not wish to be tracked. At this moment, as this is a new feature, most sites do not do anything with this information. However, Firefox is providing this option so that sites that do want to stop tracking users who opt out can do so.

Turning on do-not-track does not affect your ability to log into websites, nor does it cause Firefox to forget information about you on those sites (such as contents of shopping carts, location information or login information).

How do I turn on or off the do-not-track feature?

You can change your do-not-track preference by going to the options window, selecting the Advanced pane and checking or unchecking the box next to "Tell web sites I do not want to be tracked".