Analytics Privacy Technical

Tutorial on Top-Level-Domain Names, Cookies, and Privacy

Ignore the mouse ... and his two-letter domain name

Ever notice that when you sign into, oh, say, Gmail, you sign in at What’s up with that?

The reasons are technical, but it should be noted that when more and more traffic goes through the same domain name, you should wonder why.

Before I go off the nerd deep-end, if you don’t know what a URL is or the parts of a URL are, check out our new Wiki.

We are talking about the host portion (or domain name), of a web site. Specifically, the parts of a domain name including the top-level-domain name. So, here’s the rub:

A web site can track you across their domain and the top-level-domain

The reason is, of course, is that the rules for cookies work that way. You can set a cookie on “” and every web site that ends with that will see the same cookies.

There are some exceptions, of course, like “” which browsers understand to be a TLD as well.

That is, the following domain names all share the same cookies:


In short, Walt wants to know what you do across all of their web properties. If you are a sports person, or have kids, or watch television online, etc. They set a cookie on the “” domain name, and you are tagged across all of their web properties.

Likewise, so does Google. You may have noticed now that when you sign into YouTube, you’re sent to Google. Reason? Google tracks your usage across all of their web properties. That and they have a single authentication method for them all. So once you’re signed in one place, you are signed in everywhere.

Why do you care? I care because it’s important to protect my “privacy.” (Quotes intentional here…)

I also like to track what’s being tracked. Google sends a lot of traffic (even traffic you’re unaware of …) through The reason? They can associate all of that traffic with your web searches, your profile, and even your AdWords account.

Scary? Not yet. Just be aware of what you’re doing.

One reply on “Tutorial on Top-Level-Domain Names, Cookies, and Privacy”

Some people see things that are and ask, Why? Some people dream of things that never were and ask, Why not? Some people have to go to work and don’t have time for all that..

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