Online Tracking technologies

Cookies are the most well known and common type of tracking web tracking technologies. However, many websites, advertisers, and analytic tools use other types of technologies to track users or monitor website performance. Below are some examples of other tracking technologies.

Web Beacons and Pixels

A Web beacon, often referred to as a pixel tag, is a clear GIF or web bug, usually no more than 1-pixel x 1-pixel transparent image, that is placed on a website or in an email to monitor the behavior of the user visiting the website or receiving the email. They are often used in combination with cookies.

Web beacons work by sending information along with the request to the web server with the image. For example, when the browser connects to a site with the web beacon, the browser requests the web server to download the image – included in this request can be details such as IP address, type of browser, time of access, or previously set cookies.

Sites generally use web beacons to understand how users travel on the site and use this information to give more personalized content or make browsing more efficient and easier.

If cookies are turned off, web beacons will not be able to track a user, however, they can still be used to account for anonymous visits.


This method of tracking is generally used in conjunction with web beacons. The idea behind fingerprinting is that even with cookies turned off specific information about the user’s device, browser, language, plugins, and other settings can be sufficient to identify a single user.

Local Storage Objects

Local Storage Objects or LSOs are similar to cookies in that they are placed on a visitors browser and used to store information. Much of the same information that is stored in a cookie could be stored in a local storage object.

The main differences between local storage objects and cookies are LSOs do not have an expiration date, they store information in key-value pairs, and they have higher data limits than cookies.

Super Cookies

The term 'Super Cookie' (or sometimes Supercookie) is usually applied to tracking technologies that are not regular HTTP cookies and are stored in a different way on a user’s machine.

This makes them harder to find and get rid of - because they can't be removed using the regular privacy controls found in most browsers.

Adobe Flash applications sometimes use local file storage to optimise performance - and these files, known as Local Storage Objects, can also be used for tracking purposes, so they are sometimes labelled as 'supercookies'.

Zombie Cookies

So called zombie cookies, are technologies that are used to re-spawn regular http cookies after they have been deleted by users.

The practice of using zombie cookies is clearly intended to circumvent users’ attempts at controlling their privacy, and therefore is widely frowned upon. In many circumstances the use of zombie cookies would be a breach of privacy laws and regulations. However their use is rare.

Ultrasound Beacons

Ultrasound Beacons are inaudible signals sent out by TVs, smart phones, or other device to track users outside of the web. For example, a signal could be sent out by a TV advertisement, this signal would be a low frequency that can’t be heard by humans, however, an app in a smartphone could listen for this signal to know that a user has seen a certain TV commercial.

Ultrasound Beacons are also used to connect users in the physical and digital world by having, for example, an ultrasonic beacon installed at a store which can then be used by apps to know if a user has visited a certain store and target ads based on the user’s location.