What ELSE makes it possible for us to have a web activity profile and how can we guard against it?

Published by Alisha McKerron

In my last article,”What makes it possible for us to have a web activity profile and how can we guard against it?”, we learnt that third party cookies enable our internet browsing to be tracked and that there are various ways we can block them. However there are other methods of tracking that can be used — for example, using browser fingerprinting techniques.

What are browser fingerprinting techniques?

Just like our unique fingerprints can be used to identify us, so can a set of data related to our device — from the hardware to the operating system, to the browser and its configuration — be used to identify us. We may be surprised if not dismissive that such information has any value since the devices and software we use are pretty common. But, consider that everytime we visit a webpage our browser is communicating with the server hosting that page; consider the variable content (text, pictures, logos, live feeds etc.) of each webpage and the settings on our computer and hardware needed to render a webpage, and consider that combining all of this information into one set of data can be used to create reasonably effective identifiers. Adding more data to the mix can be used to identify increasingly more specific groups of users: for example, while 10 people may share the same browser, only 5 might share the same browser and operating system, only 3 share the same browser, operating system, and screen size, … and so on, and so forth, until ideally there’s enough data to uniquely identify one user, because nobody else shares the same device, or browser-specific attributes. 

Examples of this kind of data include plug-ins, time zone, screen size, system fonts, if cookies are enabled, language, ad blocker used, device memory, type of browser (i.e. Mozilla, Chrome, Safari etc.), screen size, screen orientation and display aspect ratio etc. 

So how is this data able to be collected? HTTP— through a series of requests and responses—allows websites (or more correctly servers serving web pages) to interact with our browser and retrieve information in the process of serving up its web page. How this is done is discussed in my last article. The information our browser receives consists of so-called Web resources (like HTML, CSS, and JavaScript files), that give instructions to our browser about what it should render on our computer screen. Whereas HTML and CSS are languages that give structure and style to web pages, JavaScript gives web pages an interactive element that engages users.  It is the existence of JavaScript that is most relevant when it comes to digital fingerprinting.

What is JavaScript?

JavaScript is a programming language that allows web designers to implement complex features on web pages. Every time a web page does more than just sit there and display static information for us to look at — displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video, jukeboxes, etc. — we can bet that JavaScript is probably involved. It is widely used across the web because it has this ability to create rich interfaces, it plays nicely with other languages, can be used in a huge variety of applications, and is relatively simple to learn and implement.  

What is relevant is that it is designed to run on our browser (i.e. client side as opposed to server side). JavaScript files are embedded in HTML documents which are served to our browser. Our browser creates a representation of the HTML document, called the Document Object Model (DOM) and JavaScript is able to manipulate the elements in the DOM in order to to make a web application responsive to the user. This makes the webpage potentially quite a lot faster (unless outside resources are required) and can reduce demand on website servers. 

Also relevant is that, since the mid 2000s, browsers automatically enable JavaScript by default and without our prior explicit permission. This is because these scripts are considered safe — they cannot be used to make evil file-destroying viruses. Also, when our browser loads a webpage it runs it inside an isolated browser tab, that prevents it from interacting with the software on our computer. But what about unintended consequences of JavaScript? 

Unintended consequences of browser fingerprinting 

It is important to point out that just running JavaScript in our browser does not in itself expose any identifying information. However, because the code executes on our computer, websites interested in identifying us can exploit certain JavaScript features for fingerprinting. They can do this by writing JavaScript that detects subtle differences in how different browsers, hardware configurations, etc. interpret and run the JavaScript code, and various JavaScript features the browser provides. 

Additionally, although Javascript is not an insecure programming language, code bugs or improper implementation can create backdoors which attackers can exploit. This is explained more fully in this article. Should we be concerned about this?

Uses of fingerprint data

Like cookies, while the result of browser fingerprinting benefits us — for example improving security, allowing us to receive services that are useful to us etc.— it is a power for good. But it benefits third parties too— such as the advertising industry with a 2020 Q2 global digital ad spend of $614 billion. Since it does so without our knowledge and at our expense, it is a serious threat to our online privacy. How can we protect ourselves against browser fingerprinting?

Protecting ourselves from browser fingerprinting

The most drastic measure we can take is to turn JavaScript off completely in our browsers. This will stop any JavaScript code from running, that detects any subtle differences in how different browsers, hardware configurations, etc. interpret and run the JavaScript code, and various JavaScript features the browser provides. But this will make home browsing more difficult; most websites rely on it and very few popular browsers will work as well without it. 

Perhaps less drastic but requiring some input on our side, would be to add plugins or browser extensions to our browser that control when we wish to turn JavaScript on or off.


I don’t think anyone will disagree that it’s important to gain an understanding of what makes it possible for us to have a web activity profile. Being careful about what JavaScript we allow our browser to run can go a long way in protecting our privacy. 

2 thoughts on “What ELSE makes it possible for us to have a web activity profile and how can we guard against it?

  1. But in your post there is a significant percentage of risk diaspora regarding the main cause and hypothetical consequences of “web profiling”.
    What should we take out from our browsing? Javascript? the browser app? configurations?
    It seems the analyses here is more of a web polemic than a best practices piece on surfing the web today


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