What Is a Browser Fingerprint and How to Prevent Tracking? ​

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FingerprintJS Fingerprinting ​

A browser fingerprint refers to a nearly unique identifier created by collecting and combining various pieces of information from your browser and device — such as browser version, operating system, screen resolution, installed fonts, timezone, plugins, and Canvas/WebGL outputs.
This allows websites to recognize or track a device/browser without using cookies.

A fingerprint is not a single data point, but a combination of multiple attributes.
Common fingerprint components include:

• User-Agent
• Screen resolution / color depth
• Timezone, language / locale settings
• Installed fonts and font rendering differences
• Enabled plugins / MIME types
• Canvas / WebGL rendering output (graphics fingerprint)
• Font metrics and text anti-aliasing differences
• Audio fingerprinting (via AudioContext)
• Hardware concurrency / number of CPU cores
• Preferred table formats, localStorage / sessionStorage support
• “Do Not Track” setting and cookie availability
• WebRTC local IP (may reveal local network addresses)

When these attributes are combined, many websites can reliably identify the same browser as having the “same fingerprint.”

Characteristics of Browser Fingerprints ​

• They persist even if you clear cookies or use private/incognito mode.
• Used for cross-site tracking, targeted advertising, anti-fraud systems, and account linking.
• Hard to defend against: many attributes are passively exposed by the browser or hardware layer.

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JA3 / JA4 Fingerprinting ​

JA3 fingerprinting is a technique used to identify TLS client characteristics.
It analyzes the Client Hello message sent during the TLS handshake and generates a hash-based fingerprint that uniquely represents the client’s implementation.

In other words:
Every browser, app, or malicious program has a different set of TLS parameters when establishing an HTTPS connection,
and these differences create a kind of “network-layer fingerprint.”

How JA3 Works ​

JA3 extracts and concatenates the following 5 fields:

1. SSL Version
2. Cipher Suites
3. Extensions (TLS extensions)
4. Elliptic Curves (supported curves)
5. Elliptic Curve Formats

For example, these fields might form the string:
771,4865-4866-4867,0-11-10-35-16,23-24,0

Then the string is hashed using MD5, resulting in a JA3 fingerprint such as:
e7d705a3286e19ea42f587b344ee6865

JA4 is an improved version of JA3 (proposed by Fox-IT / Salesforce, gaining popularity since 2023).
It addresses several JA3 limitations, such as:

• JA3 is sensitive to field ordering (e.g., changing the order of cipher suites results in a different fingerprint).
• JA3 only applies to client-side (Client Hello) messages.
• JA3 cannot easily distinguish between slightly modified implementations.