How to Control Web Cookies and Boost Online Privacy
Don't like being tracked on the web? The right browser settings can help.
Odds are that your computer’s browser is full of cookies, tiny files left behind as you go from website to website. Mine is. My personal machine has close to 5,000 cookies.
Some of the web cookies on your machine are used by big advertising companies looking to gather and store information about you—what you shop for, which sites you visit, and so on. That can feel like a violation of your privacy and make you think you should dive in and delete them all.
But other cookies contain important information that makes your web experiences smoother. Which is why you really shouldn’t dive in and delete them all.
How Do They Work?
When Deckelmann visited the retailer's website, it deposited a number of cookies on her computer, in a location determined by her browser. Some of those cookies—called first-party cookies—came from the domain that she saw in the URL at the top of the browser window, such as Amazon.com or Lowes.com. (We'll discuss “third-party” cookies below.)
The first-party cookies left by the retailer carried information such as an indication that she had logged in successfully. They may have recorded her location (to help the website display the right language and currency) and what she placed in her shopping cart.
But how does the website use that information?
Each time you go to a webpage, your browser sends out a request for the files needed to display the page. And along with that request goes a copy of every cookie that originated with that domain. The browser sends Amazon.com the cookies left by Amazon.com, while BestBuy.com gets the cookies left by BestBuy.com, and so on.
Lots of those cookies expire when you close the browser, but not all of them.
When Deckelmann came back to the site the next day or the next week, the browser sent back copies of the remaining cookies. That’s how the site seemed to know who she was, and what she’d done during her last visit.
Without first-party cookies, websites would seem a lot stupider.
So What's the Problem?
We’ve only been talking about first-party cookies. But during Deckelmann's visit to the retail website, other companies may have deposited their own, third-party cookies.
How did that happen? Well, a webpage is made up of many files and little bits of code. Many of those bits and pieces come from the retailer itself. But other elements, such as ads and social media buttons, come from other companies.
A huge percentage of all the ads you see online are handled by DoubleClick, which is owned by Google, so let's use that company as an example. When you see an ad embedded in a webpage, there's a good chance it's coming from the domain DoubleClick.net. And the advertisement may carry cookies along for the ride.
Next time you go to any site with elements originating on DoubleClick.net, your browser sends DoubleClick a copy of all its cookies. If you visit many websites that contain chunks of DoubleClick content, your browser supplies the company with a steady stream of cookies.
And remember, DoubleClick.net is just one example of the many domains that supply elements to webpages and leave cookies on users' machines.
That's why the entire internet seemed to know instantly that Deckelmann had been shopping for sinks.
As Oppenheim says, "From a consumer perspective, there's a big difference between first-party cookies and third-party cookies."
How Targeted Ads Work
Do you often see online ads that relate to your likes and hobbies? On the "Consumer 101" TV show, Consumer Reports expert Thomas Germain explains to host Jack Rico what targeted ads are and how they work.