Worried about your online privacy? If not, you should be: there’s a lot of money to be made in figuring out where people go on the web, when and why, and companies are scrambling to find new, sneakier ways to follow everything you do.

And don’t think you’re necessarily safe because you’ve installed a cookie-blocking browser extension, antivirus software, or the best VPN, either. Cookies were recognized as a threat to privacy over 25 years ago, and tracking companies have been developing stealthier privacy breaching technologies for a very long time.

Browser fingerprinting is probably at the top of the “most dangerous” tracking charts right now, because it’s precise, hard to spot, and many browsers do next to nothing to keep you safe. In this article, we’ll explain how the technology works, show you how to test it for yourself, and point out free tools that will help you stay safe.

What is Browser Fingerprint?

Tracking users online involves finding and assigning them a unique identifier – a tag that ensures the advertiser (or anyone else) can recognize them as they move around the web.

This may involve setting a cookie, verifying your IP address, or simply persuading you to stay logged in to a social network or other accounts. But users are increasingly aware of this and know how to fight back. They can change their browser settings to control or block cookies, for example; install a VPN to hide their IP address or use private browsing to limit what others can see about them.

Browser fingerprinting takes a very different approach. The basic idea is that even if you think your setup is very, very common – you’re using Chrome on a Windows 10 laptop, for example – in reality your device differs from others in many ways (precise browser version and operating system, time zone, installed applications, precise hardware details, etc.). Combine enough of these details and it’s often possible to create a unique fingerprint for your device.

It’s a stealth technology that has a lot of appeal for tracking companies, not least because it’s so hard to block. You can use a VPN, disable cookies, or use private browsing 100% of the time, while being tracked. And most browsers don’t have obvious settings to help you stay safe.

Do not panic: you can take useful measures. But to understand them, we first need to take a closer look at what fingerprinting actually entails.

How Browser Fingerprint Works

Visit a website and it’s easy to think your device is just like any other. If you use Chrome, for example, then you’re one of the countless millions, and it’s tempting to think you’ll seem like part of the crowd.

The problem is that websites don’t just see you as “a visitor using Chrome”. Some well-chosen JavaScripts allow them to detect a multitude of details about your system, making you much more identifiable.

For example, after collecting your information, a website may go beyond identifying you as a “visitor using Chrome” to see you as “a visitor using Chrome…whose preferred language is US English; and is located in the PST time zone; and has cookies disabled; and is running Windows, on a device with 8 browser cores, 16 GB of RAM and a screen size of 1920 x 1060; and uses a certain graphics card and a driver; and has those specific system fonts installed.’ It’s likely that there will be others with the same fingerprint as you, but more “countless millions”, and using more advanced techniques can come even closer to providing a unique identifier. .

Canvas Fingerprint, for example, sees the tracker draw an intricate pattern of shapes, colors and text (invisible to the user), then perform pixel-level analysis of the result. This may vary depending on your graphics card, firmware, operating system, drivers, etc., and we’ve seen claims that canvas fingerprints can help identify users with a probability of 99.5%.

Similar technologies include WebGL tracking (more graphics tricks) and Audiocontext, where a tracker plays a small sound sample and measures the results. None of these will necessarily accurately identify you, but put enough together and you’re likely to have a unique (and highly traceable) browser fingerprint.

How can I test browser fingerprinting?

Browser fingerprinting might seem complicated, but you don’t need to be an expert to understand the key details. Just visit one or two fingerprint test sites and you will quickly get an idea of ​​how it works and how effective it is.

Cover your tracks (opens in a new tab) is a free service run by the digital rights group Electronic Frontier Foundation. Visit the site, click Test your browser, and within seconds it will show you the various details that make up your fingerprint and explain what they mean.

Search the site for ‘Protect yourself from fingerprints?’ verdict at the top of the page. This claimed that our browser’s fingerprint was unique “among 217,097 tested over the last 45 days”, showing that the fingerprint could be used to effectively track our browser online.

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am i unique (opens in a new tab) collects and displays many other fingerprint details, handy for showing exactly what the technology can do. Like Cover My Tracks, it will also tell you if you are vulnerable to tracking. And again we were, with the site claiming our fingerprint was unique out of the 561,688 in its database.

Browser leaks (opens in a new tab) has a detailed web fingerprinting page, including a graph showing how the same text can vary on different systems, and surprisingly simple JavaScript code showing exactly how it’s done.

Some fingerprint techniques are so smart that they can detect when you try to bypass them. When we visited GoLogin’s (opens in a new tab) site, it not only collected and displayed details about our configuration, it also detected our use of the VPN, warning: “it looks like you are spoofing your location”. While VPNs can offer real benefits in many areas, it shows that sites may be able to recognize that you’re using them, and that in itself could set you apart from the crowd.

How to Block Browser Fingerprint

Preventing browser fingerprinting entirely is difficult, as the technology can use many different pieces of information about your system to create a unique identifier. But there are several ways to reduce the risk:

• Use Firefox, for example, and you’ll immediately benefit from its enhanced tracking protection that blocks known fingerprints from probing your system. And while it’s still labeled as “experimental,” its fingerprint protection (opens in a new tab) The feature adds additional functionality by changing how your fonts, time zone, browser version, language, and other details are reported to websites.
• The Brave browser has even more sophisticated tools, with a shield (opens in a new tab) feature that can block canvas, WebGL, and many other types of fingerprints (the company explains all in its fingerprint defenses (opens in a new tab) page).
• Chrome doesn’t have the same built-in functionality, but as always there are browser extensions to fill in the gaps. Canvas Fingerprint Defender (opens in a new tab) adds a small amount of random noise to canvas results, for example, ensuring that sites cannot get a consistent fingerprint. It’s very simple, there is nothing to configure, it works.
• Canvas Blocker – Protect Fingerprints (opens in a new tab) does something similar, but is technically smarter and has more features, including the ability to allow fingerprinting on specific domains (handy if web blocking breaks a legitimate site). To see this in action, install Canvas Blocker – Fingerprint Protect and revisit the BrowserLeaks (opens in a new tab) canvas fingerprint site. We found that the page flagged a new random fingerprint every time we refreshed it, ensuring we couldn’t be tracked. The extension even warned us about the tracking attempt, a nice touch while you’re testing.

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• Blocking canvas fingerprints is a good start, but it won’t protect you from trackers using other technologies. Trace (opens in a new tab) is a powerful Chrome extension that blocks canvas, WebGL, audio, and hardware fingerprinting, as well as many other privacy threats. There’s a lot here for a free plugin, but it can be complex and best suited for more technical users.
• Avast AntiTrack Premium (opens in a new tab) is a comprehensive Windows and Mac application that works to block fingerprinting and web tracking across all your browsers. It has stacks of features and is very easy to use, but it is expensive.

If you’re not sure what to do next, we recommend starting with a free browser extension. Search your store for the keyword fingerprint, install anything that looks promising, and use the test sites we list above to confirm that they are now giving you a random fingerprint.

This can cause problems later, if your anti-fingerprint tool blocks a feature that a legitimate website needs. Keep that in mind and add “turn off fingerprint blocker and try again” to your standard list of web troubleshooting steps.

However, if you only follow simple steps, like with the Canvas Fingerprint Extensions above, you’re unlikely to run into any problems. You’ll be able to carry on with your usual web activities while your new tools work, automatically blocking at least some web fingerprinting and helping to preserve your online privacy.