When you open any website, your browser reveals surprisingly much about you - usually without you ever noticing. A site can see your public IP address, your device type, your operating system and dozens of other details that together form a unique identifier. In this article we explain exactly what a website knows about you and how to defend yourself against unnecessary tracking. If you want to see your own data live, try our free What Websites Know About You tool, which detects everything right in your browser and stores nothing.

What Your Public IP Address Reveals

Your public IP address is a number assigned by your internet provider, and it is how the whole web sees you. Think of it as the return address on an envelope - without it, a server could not send a reply back to you. From your IP, a website learns which provider you use and roughly which city or region you are in. Nobody can read your exact street from it, but a guess down to city level is often correct.

An IP address on its own is not your name, but combined with other data it helps websites and advertisers link your visits together. If the topic interests you in more depth, read our separate article What Is an IP Address, where we explain how it came to be and the difference between a public and a local address.

Browser Fingerprint: Your Digital Identifier

The browser fingerprint is one of the least visible yet most effective tracking methods. It works by collecting dozens of small pieces of information about your device: your graphics card model, the list of installed fonts, screen resolution, browser version, language settings and the way your device renders graphics.

Each of these data points is ordinary on its own, but their combination is so unique that it can identify you among millions of other users. The most insidious part is that a fingerprint needs no file stored on your device - it is recreated on every visit. That is why clearing your cookies does not remove it, and even private browsing mode often fails to stop it.

Cookies and Tracking Scripts

Cookies are small text files a website saves in your browser. The essential ones keep you logged in or keep items in your shopping cart. The problem lies with so-called third-party tracking cookies, which advertising networks and analytics tools embed into the page.

Thanks to them, the same advertising network can recognise you across different websites and build a profile of your interests. If you have ever noticed that a product you viewed in one shop then follows you with ads everywhere else, this technology is the reason. Besides cookies, various scripts and tracking pixels watch you too - tiny invisible images that report when you opened a page or an email.

What a Website Sees Even Without Logging In

Many people assume they are anonymous as long as they do not log in. The reality is different. Even on a completely unfamiliar site where you never entered an email, your browser automatically sends information about your operating system, browser type and version, screen resolution and colour depth, your language, your time zone, and whether you are on a computer or a phone.

A website can estimate your hardware performance, the number of processor cores and the amount of memory. It knows which page you came from and where you click. You can view all of this data live in our What Websites Know About You tool - you will see exactly what every site you open sees.

How to Defend Yourself Against Tracking

You will never be completely invisible on the web, but you can significantly limit how much is tracked. The most effective approach is to combine several measures:

  • An ad and tracker blocker (such as uBlock Origin) stops most tracking scripts and third-party cookies before they even load.
  • A VPN hides your real IP address and changes your apparent location. It does not protect against fingerprinting, so combine it with other tools.
  • Browser settings: turn on third-party cookie blocking, tracking protection and the “Do Not Track” header. Some browsers (such as Firefox or Brave) have built-in fingerprint protection.
  • Clearing cookies regularly and using a separate profile or private window for more sensitive browsing.

No single measure is perfect, but together they give back a large part of your privacy. The key is knowing what to focus on - and a look at your own data shows you exactly that.

In the European Union, the GDPR regulation gives you the right to know what data websites process about you and what they use it for. That is exactly why you see cookie banners when you enter a site. The rules are clear: a website needs your consent only for cookies that are not strictly necessary for the site to function, mainly tracking and advertising ones.

The banner must let you refuse cookies as easily as accept them - a “Reject all” button should be just as visible as “Accept all”. Consent must be voluntary, and you can always withdraw it later. Essential cookies that keep you logged in or hold your cart work without consent, because the site would not function without them. Next time you see a banner, you will know what you can safely refuse without ruining your browsing experience.

If you want your privacy and browser settings sorted out properly, get in touch, we are happy to help.

This article is part of our Cybersecurity overview.