Canvas Fingerprinting: What You Need to Know

Key takeaways:

• Canvas fingerprinting tracks users by analyzing how their browser renders graphics on the HTML5 canvas element.
• Websites use hash codes based on the user’s device to create unique fingerprints.
• It’s an invisible tracking method that cannot be cleared or deleted easily, like cookies.

Online tracking has evolved significantly over the years. Websites and advertisers constantly look for new ways to identify users and monitor their online activity, especially as increasingly more people tend to use incognito mode or VPNs to hide their true identity.

One of the most advanced techniques is canvas fingerprinting. It’s a method that doesn’t rely on cookies and analyzes how a browser renders graphic elements instead. Canvas fingerprinting is often used without the user’s knowledge since it’s not like cookies, which you must accept or reject.

In this article, you will discover what canvas fingerprinting is, how it works, how it impacts privacy, and how you can reduce your exposure.

What Is Canvas Fingerprinting?

Canvas fingerprinting is a type of browser tracking that uses the HTML5 canvas to create a unique digital fingerprint for each visitor. It allows websites to identify users based on how their browser renders an image, instead of relying on traditional cookies that are now easily avoidable.

Unlike cookies, which store data collected on the user’s device, canvas fingerprinting operates passively. The technique extracts details from a browser’s graphics processing capabilities, such as:

• Screen resolution
• Installed fonts
• Operating system
• Browser version
• Graphics card

Since no actual data is stored on the device, it is difficult to detect or delete, while deleting and clearing cookies is easy. Canvas fingerprinting works by exploiting the minor rendering differences that appear due to variations in hardware and software configurations.

How Canvas Fingerprinting Works

Since it could seem like a difficult process, let’s break it down into a step-by-step process to understand how canvas fingerprinting operates:

• A website runs JavaScript code that activates the canvas element.
• The user’s browser is instructed to draw a hidden image or text on the HTML5 canvas. It could be a rectangle with some lines or any other graphic element.
• The rendering process depends on the user’s device, including their graphics, operating system, and installed fonts.
• Once the image is rendered, the output is converted into a hash code, which is a unique string of numbers and letters.
• This new string of characters acts like a fingerprint and allows websites to track visitors even if they delete cookies or use incognito mode.

Each device and browser combination produces a slightly different fingerprint. Since no two setups are exactly the same, websites can reliably identify users across multiple sessions.

The Fingerprint Canvas Explained

The effectiveness of canvas fingerprinting lies in how different devices process graphical data. Several factors influence how an image is rendered:

• Graphics card

The GPU in the device affects how colors, shading, and anti-aliasing are applied.

• Operating system

Windows, macOS, and Linux all handle rendering slightly differently.

• Browser version

Different versions of Chrome, Firefox, and Edge interpret the canvas element in their own way.

• Installed fonts

The availability of specific fonts can impact how text is drawn.

• Screen resolution

It determines the size and detail of the output image.

After rendering, the browser converts the image into a string of characters. Since this code is unique for each configuration, it can be reliably used for tracking.

Canvas Fingerprinting vs Cookies

You are probably familiar with cookies, but canvas fingerprinting operates in a completely different way. Here’s how they differ:

Since cookies can be easily cleared, many websites prefer canvas fingerprinting to track visitors without leaving a trace.

Why Use Canvas Fingerprinting

Companies and websites use canvas fingerprinting for several reasons: security, personalization, fraud detection, and more. Let’s break down how canvas fingerprinting helps with each of them:

Security

Canvas fingerprinting helps detect bots and automated scripts that could slow down the website or pose other cyber threats. Also, it identifies suspicious behavior, such as multiple accounts from the same device.

Personalization

Especially useful for marketers, canvas fingerprinting also enables better personalization. In turn, companies can serve customized content based on browsing history, and ad platforms can serve more relevant ads.

Fraud Detection

Banks, financial services, and healthcare institutions use canvas fingerprinting to spot unusual login attempts. It helps prevent identity theft and fake accounts from spamming these sensitive systems.

To briefly sum up, by analyzing the user’s browser, companies and institutions can create accurate digital fingerprints to identify users and track their behavior.

Privacy Implications

The biggest concern with canvas fingerprinting is that it happens without user consent. Unlike cookies, which require user approval in many countries, canvas fingerprinting operates invisibly.

When combined with other tracking methods, websites can build highly detailed profiles of user visits across multiple sessions. Even if a user takes steps like clearing cookies or changing their IP address, their device still produces a unique string of characters.

What’s most disturbing is that the vast majority of people don’t realize how canvas fingerprinting works. As a result, they may not take the required steps to prevent it.

Mitigating Canvas Fingerprinting: Canvas Fingerprint Defender

Preventing canvas fingerprinting completely is difficult, and it would require extensive coding knowledge, but you can reduce its effectiveness in some ways. Here are some tools and techniques that can help:

• Privacy Badger

It detects and blocks third-party trackers, but it may not block all forms of canvas fingerprinting.

• Adblock Plus

This extension is primarily designed to block ads, so its capabilities against canvas fingerprinting are limited, but it still can block some known tracking scripts.

• Canvas Defender

This extension generates a fake fingerprint, preventing accurate tracking.

• Canvas Fingerprint Defender

It spoofs fingerprint values and confuses trackers by altering the hash code.

• Tor browser

It’s an anti-detect browser that notifies users when a website attempts to access the canvas element, which allows you to block fingerprinting attempts manually.

Testing Your Browser: Browserleaks Canvas

If you’re curious about your browser’s fingerprint, Browserleaks Canvas is a tool that shows how unique your fingerprint is . It analyzes details like:

• Screen parameters
• Fonts installed
• Graphics card specifications
• Uniqueness of your code

By running a test on Browserleaks Canvas, you can see how websites identify users using canvas fingerprinting.

Future Trends

A new approach called DrawnApart uses AI to analyze the unique characteristics of a device’s GPU rendering process, which enables the identification of individual devices, even among those with identical hardware and software configurations. It makes fingerprinting even more effective.

However, as tracking technology evolves, so do countermeasures. Future browsers may include built-in anti-fingerprinting features, which could reduce the effectiveness of canvas fingerprinting.

A couple of examples are the Tor and Brave browsers that have some anti-fingerprinting measures like canvas image extraction blocking and fingerprint randomization.

Conclusion

Canvas fingerprinting is a powerful tracking method that doesn’t require cookies and doesn’t notify the user. It analyzes the HTML5 canvas to create a unique fingerprint for each user’s device. Unlike cookies, it cannot be deleted or blocked easily.

To protect yourself, consider using Canvas Defender or Canvas Fingerprint Defender to generate a fake fingerprint. Additionally, tools like Browserleaks Canvas can help you understand your exposure to canvas fingerprinting.