Hi MozzieBob, I don't know whether I can answer all of these questions, but here is my understanding. First, a general description: Firefox's Tracking Protection feature uses a list of tracking servers (e.g., google-analytics.com). If a server is on the block list, Firefox will NOT send requests to that server which are embedded in pages you visit. If Firefox does not send a request, it has no reason to send cookies that it may have stored from that server previously. It also will not receive any response instructing Firefox to set new cookies for that server. Cookies don't come into play if no request is sent. This is a supplemental type of protection that coexists with cookie management strategies and tools. <blockquote> 1. Do I need to clear existing cookies to remove the myriad of sites already tracking me before turning on tracking protection? Or, will turning it on do an immediate filter on my existing cookies? </blockquote> The Tracking Protection feature does not edit, filter, or remove cookies. It prevents connections to tracking servers. From time to time, you probably will need to allow tracking on some sites in order to get useful features of the page to work. (Well, arguably useful!) For example, some sites link the previous and next buttons on their slideshows to Google Analytics. When GA is blocked, you can't advance the slide player. If you go ahead and make an exception, then Firefox will send the site's previously set cookie. If you want to avoid this scenario, you need to take other steps, such as clearing, blocking, or isolating unimportant cookies. Trackers are nearly always "third party" requests, meaning they are to servers other than the one listed in the address bar. You can look at third party cookie settings or add-ons that manage cookies. One of the simplest tools to limiting tracking via third party cookies is to reduce their lifespan. Firefox has a setting to limit that to your current session. Exiting and restarting Firefox should clear these third party cookies. Note that this is not retroactive, so you may need to remove older cookies before it has much effect. (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk. (2) In the search box above the list, type or paste '''third''' and pause while the list is filtered (3) Double-click the '''network.cookie.thirdparty.sessionOnly''' preference to switch the value from false to true <blockquote> 2. Will turning off tracking stop sites that I want to retain login information for from retaining the "login" cookie infor i.e. are we close to a full "cookie block" with anti-tracking? Or does FFox have some creative algorithm (or list) that allows it to distinguish between tracking cookies and less offensive cookies? Concurrently, is there a way to allow a "tracking cookie" if I need it to retain information for a site I'm comfortable with? </blockquote> I don't think any server you ''want'' to recognize you is likely to be on the Tracking Protection block list unless your job involves web analytics or web advertising. Anyway, there is no feature to fine-tune the block list or make partial exceptions. You can use an add-on instead if you want to allow specific tracking servers. <blockquote> 3. One specific tracking question: Will eliminating tracking cookies stop (specifically) Google's cross site advertising, where you look at a product on site A (who shares that info via google) and then a little later google's advertising mechanism pops up those products when you're at site B? </blockquote> Many Google sites are used widely for legitimate functionality and therefore cannot be blocked by Tracking Protection. You will need to consider other features to handle this scenario, whether related to cookies or related to ads.