A Short Primer on Tracking Cookies


Tracking cookies are used for a variety of reasons. Both the websites you visit and your own browsers can cause a cookie to be “set.” Cookies can also be either a first-person cookie or a third-person cookie to be placed on your computer.

We’ll take a look at some of the reasons that cookies are used first. We’ll follow that with a short discussion of the differences between servers and browsers setting cookies, and finally, we’ll take a look at first- and third-person cookies.

What Are Cookies and What Do They Do?

In a nutshell, tracking cookies are small files that are stored on your computer that tell either a browser or a server something about you, or that create a link between you and the website being visited. If a browser sets the cookie, the information stored could be passwords and usernames to make logging into controlled websites easier. They can also contain information such as language preferences, location, and privacy settings.

However, websites can also set cookies for those reasons. Retail websites also use them for storing information regarding pending purchases, pages visited, and items looked at. Sites like Digital Landing and Yahoo often use them to determine what ads to show you.

Tracking Cookies Can Be Either Server-Side and Client-Side

Cookies are known variously as tracking cookies, HTTP cookies, web cookies, and browser cookies. A cookie can be set by either a web server or a web browser. A cookie is “set” when a page makes a request for information when visiting a website. When a server is making the request for a cookie to be set it is known as a server-side cookie. Conversely, when the browser makes the request it’s known as a client-side cookie.

Cookies Like to Party!

Come join the party with the cookies! These guys love first and third parties. Seriously, tracking cookies can be either first-party or third-party cookies, depending on who sets them. A first-party web cookie will be set either by your browser or the server that runs the site you’re visiting. You can tell a cookie is a first-party cookie because the cookie/filename has the name of the site being visited in it. For instance, a cookie set by the Digital Landing website will have digitallanding.com in its name.

Third-party cookies, on the other hand, come from a source other than your browser or the site being visited. These usually come from ad exchanges. You can identify a third-party cookie because the name will be different from the name of the site being visited. For example, if some other website asks to set a cookie on your computer while visiting Digital Landing, you might see an ad from Google Ads with a filename googleads.com in the name of the file.

Without going into all the boring technical details, the mechanism for third-party cookies is different also. Instead of the server or browser directly setting the cookie, a call is made from what is known as a web beacon to the server. When this call is made, a request is made to place pixels (imagery) on the page being viewed and where to place it.

Cookies Work in Most Browsers on Mobile Devices

Cookies can also be set when you’re using a mobile device to browse the web. However, due to differences in programming and how mobile requests are handled compared to desktop requests, how cookies are handled on mobile devices differs. They still store the same information as your desktop browser, but they’re not normally able to share information across devices or across different browsers.

A Short Explanation of the Differences Between Desktop and Mobile Devices

When you’re on a desktop/laptop computer, you usually only visit websites in your web browsers. However, with our mobile devices, we’re visiting websites from within browsers, messaging, and apps. The problem is that these programs all handle website traffic and information differently.

Browsers on mobile devices, as stated above use cookies. However, most mobile apps use something called webview to track visitors. Due to the way webview works, such as the fact that it ignores page load errors, the information gleaned here can’t be shared across devices or apps.

If you’re interested in something more in-depth and technical, the Interactive Advertising Bureau is an excellent source of information for online website visitor tracking.

Photo Credit: Hada del Lago