The Secret Science of Website Fingerprinting
Published on July 4, 2025
When you hear about website fingerprinting, it sounds like the plot of a spy movie. Unfortunately, it's real—and rapidly evolving. With website fingerprinting, websites and analytics companies can identify and track users (and their devices) and render profiles based on sensitive information. While cookies can be deleted and/or blocked by users, fingerprints rely on non-removable device or browser characteristics to build out a profile.
In this post, we'll discuss what website fingerprinting is, how it works under the hood, website fingerprinting meaning, and where it's used across various industries today.
1. What Is Website Fingerprinting?
Essentially, website fingerprinting is the process by which various attributes of a device are collected and processed to create a collated profile or "fingerprint" ultimately. These fingerprints are used to track a person across various websites (even in incognito) and across different sessions with the same person.
Some commonly fingered devices include:
- Browser and version
- Screen resolution and color depth
- Installed Fonts
- Operating system
- Time zone / system language
- WebGL / Canvas drawing
- Touch screen support
- Audio context fingerprints
Because most users do not have the same combination, research shows that up to 94% of desktop sessions are unique.
2. How It Works Under The Hood
Website fingerprinting occurs through background scripts—mostly JavaScript—that occur naturally when browsing a website. These scripts call to environment variables through APIs like:
navigator.userAgentnavigator.platformwindow.screenIntl.DateTimeFormat().resolvedOptions()- HTML5
<canvas>element - WebGL shader rendering
At the end, a hash is computed from various attributes (i.e, SHA-256), and the fingerprints look like:
5e40e4bde7cc57f48f1e6d33e25a6af4f4e54c22b70f12b9e56a8c7b21ce1ef1
This hash gets stored on the relevant server or analytics company database, and can be used to identify the user again—even when they've cleared cookies.
3. Where It's Used in 2025
Fingerprinting is used across industries, for reasons such as:
- Ad Tech: To follow users across domains
- Fraud Detection: If the same device ID shows up during a login and a payment attempt, the activity might be flagged
- Account Recovery: In place of 2FA, some sites may allow a fingerprint ID recovery to reload access to the account
- Content Layout Personalization: Websites can create different iterations for iPads, desktops, etc.
But one of the biggest places fingerprinting is used is within cybersecurity with the ability to note when someone has changed their user agent or other internal device characteristics while accessing specifically targeted accounts that are often hacked.
4. Privacy Risks
While this is all valuable (and practical) use cases, there are legitimate privacy concerns:
- Unblockable: Unless someone discovers a way to ensure blocking of all relevant fingerprinting services, they cannot prevent it
- Invisible: Most sites do not acknowledge their fingerprinting in relevant privacy policies
- Irreversible: Fingerprints are unchanged by VPNs and private browsing (although this does change IP addresses)
Certain browsers (Firefox and Brave) now have anti-fingerprinting features, but this prevents site functionality for many.
5. How To Check/Protect Yourself
🔍 Use Our Fingerprint Check Tool
Take a visit to https://help.affilfinder.com/Free-Tools/fingerprint and see what exactly is known about your device that's available.
🛡️ Protection Considerations:
- Privacy-based browsers (Brave, Tor)
- Anti-fingerprinting features enabled
- Browsers that allow extensions (Google Chrome) so users can download and use Privacy Badger or uBlock Origin to keep tracking at bay.
- Clear cache and user-agent settings regularly so that datasets processed for hash creation get refreshed.
Conclusion
Website fingerprinting is an invisible act of great power on today's web. Understanding the process and how it works might help you better maneuver your own online privacy considerations day-to-day. Check out our live test tool and see how vulnerable you really are—you may be shocked!