If you’ve ever paid attention to those small ads floating around your favorite site, you might have noticed that they’re eerily specific - almost as if they’re tailored especially for you. That’s because they are.
 
Learn how companies collect your information, how they use it, and how you can manage your privacy online.

How do companies track me?

You’ve probably heard of “cookies,” but it’s not entirely obvious what they are or what they do.

When you visit a website, it will scan your computer for an identifying code specific to that site. If it doesn’t find one, it will create one for you and place it in your web browser. This code is the “cookie”. When you next visit the site, it can find the cookie to determine which user you are.
 
For example, say you visit Weather.com and search for the weather in Columbia. The site will place a cookie on your computer; “LocId:65202”. The next time you visit, it can spot this cookie and automatically bring up the Columbia weather without having to ask where you are.
 
Cookies are a simple way for websites to gather anonymous information. Many (if not most) sites use cookies to track visitor information, including whether you’ve been there before, what pages and preferences you set, and how often you visit. Generally, these cookies are benign, limited to a single site, and meant for your convenience. However, there are some sites that offer or sell this information to others.
 
For instance, Weather.com knows that you’re in area code 65202. Alone, this isn’t very useful information. But say that another site knows your age. Perhaps you’ve been shopping online for clothes; that site can reasonably infer your gender. Online advertising companies can purchase all these scattered bits of data and piece them together to create a cross-site profile. While it’s still technically anonymous, a business will know enough about your online behavior to send you targeted ads.
 
For some individuals, this can be annoying or even downright creepy. This can also lead to some privacy issues for those with shared computers. (Imagine borrowing a friend’s computer and seeing nothing but ads for toupees and hair loss products!)

How can I increase my privacy online?

Before signing up with a service, check their privacy policy and opt-out features if they have any. There are often separate checkboxes at the end of registration forms for things like email lists, third party sharing, and data collection.

There are also settings you can adjust in your web browser. Check your cookies to see what sites have information saved about you. If you’re not familiar with a cookie, delete it. If you’re extremely cautious, you can disable cookies altogether. Keep in mind that some sites need cookies to function; you can always delete the cookie when you’re done.

Resources

See what demographic information Google has on you, or opt out of Google’s interest-based ad network:

www.google.com/settings/ads/onweb
 
Yahoo offers a similar page. You can also adjust your demographic information or opt-out entirely:
 
info.yahoo.com/privacy/us/yahoo/opt_out
 
See how Facebook uses your data to create personalized ads:
 
www.facebook.com/about/privacy/advertising