Remember that color from the start page?
This color is your individual fingerprint.
It's based on all the parameters you just provided and as long as the configuration stays the same, the color will be the same. Try it on other devices and browsers, you will see different results. By the way, there are over 16 million different color possibilites...
Entropy and why you are trackable
By moving through the internet, you leave traces on your journey all around the place like fingerprints on objects when you interact with the «physical» world. Some of them are surely intentional – like putting information on social networks or filling out your data on contact forms – other happen automatically from a technical point of view. By visiting a web page your computer starts communicating with other computers and tells them all kind of stuff about your machine, like your operating system, preferred language, installed fonts, screen resolution and the current version of the software you use. By itself, all this data doesn't reveal anything particular about your person or your identity, but the problem lies within mathematics and the uniqueness of all the data combined.
Let's say you have to identify yourself as an individual within all humans currently living with as least information as possible. How much data do you need? And what data do you chose? Think about your first and last name – is it truly unique? How many people might live within your neighbourhood, city or even country with the same name? Probably more than one, and your name usually contains quite a lot of letters as well, so let's scrap this example. Let's try the same with your birth date: surely there are some people with the same birthday and year as you, but how many of them are living within a couple of kilometres around your current residency? Now we're getting closer: the birthdate is already quite short and handy – using 8 digits only – however, it's not sufficient to identify yourself as an individual yet. So let's add your zip code to that information (additional 4, 5 or 6 digits) and your sex (usually 2 possibilities, therefore 1 digit) and we have enough data to theoretically identify you within all 8 billion people currently living. So about 12 to 15 digits are enough to give you an unique number. Naturally, the more we add to this information, the more unique you become.
But now to the important part: All of this data (birthdate, zip code and sex) is usually considered as anonymous, especially as discrete values. By combining them, one can suddenly become identifiable and therefore traceable.
Now, the same goes for your computer: By using different, tiny fragments of information in combination, you suddenly get traceable and marked as one under millions or billions of internet users. The more information you reveal, the more you stick out of the crowd. Or from the other point of view, the more you look like others, the more anonymous you get.
There lies the root of the problem: advertisers, hackers as well as governments and their powerful agencies are more than interested in identifying and tracking you. Sure, on some occasions you freely chose to by providing all kind of personal information and there you might even don't care at all – even though it's potentially dangerous as well. Anyway, the passive method happens even without your permission. So, by just surfing the web, you reveal more about yourself than you might be aware of. Eventually these breadcrumbs, footprints or fingerprints can lead anyone with a particular interest right into your personal information and ultimately reveal your identity.
Luckily, there are methods, tools and techniques to cover yourself as much as possible, wether you try to blend in as much as possible, deactivate unnecessary features or use encryption for your communication.