Browser Fingerprinting Explained: 11 Signals That Reveal Your Identity

Every time you visit a website, your browser quietly shares dozens of technical details about your device and configuration. Collectively, these details form a browser fingerprint — a near-unique identifier that can track you across the web without cookies. Understanding browser fingerprinting is essential for anyone concerned about online privacy, and it is the foundation of tools like our Claude Code China User Scanner.

What Is Browser Fingerprinting?

Browser fingerprinting is a technique that collects information exposed by your browser and combines it into a profile. Unlike cookies, which can be deleted, a fingerprint is derived from your device's inherent characteristics. Two users with different hardware, software, and settings will almost always produce different fingerprints, making it possible to distinguish and track them.

The 11 Signals We Check

1. System Timezone (Weight: 26)

Your operating system timezone, read via Intl.DateTimeFormat. This is the exact same signal Claude Code uses for China user detection. Zones like Asia/Shanghai immediately reveal your location.

2. Browser Language (Weight: 20)

The language list from navigator.languages. Having zh-CN at the top strongly signals a Chinese-speaking user, while its presence anywhere in the list still provides a weaker signal.

3. Installed Chinese Fonts (Weight: 17)

Using canvas width-probing, we test whether fonts like Microsoft YaHei, PingFang SC, SimSun, or Source Han Sans are installed. These fonts come pre-installed on Chinese-market devices.

4. Intl Locale (Weight: 8)

The locale resolved by Intl.DateTimeFormat for date and number formatting. A locale of zh-CN confirms Chinese regional settings.

5. Timezone Offset (Weight: 6)

Whether getTimezoneOffset() returns -480 (UTC+8). This is a weaker version of the timezone check — many countries share UTC+8, but combined with other signals it adds confidence.

6. Emoji Rendering Style (Weight: 5)

The OS vendor guessed from the user agent string. Different operating systems render emoji differently, providing a loose correlation with user demographics.

7. WebGL Renderer (Weight: 5)

The GPU model exposed by WEBGL_debug_renderer_info. Some GPU models like Huawei's Kirin or other domestic chipsets are strongly associated with China-market devices.

8. Screen Resolution (Weight: 4)

Certain display resolutions are more common on laptops and phones sold in the Chinese market, such as 2560x1600 found on Huawei MateBook series.

9. Network Info (Weight: 3)

The navigator.connection API exposes network type hints. This is a weak auxiliary signal.

10. Browser Plugins (Weight: 3)

Plugin count and hardware concurrency as environmental fingerprints. Modern privacy-focused browsers often normalize these values.

11. Privacy Signals (Weight: 3)

Do Not Track and Global Privacy Control settings. Chinese users rarely enable GPC, so the absence of these privacy signals provides a weak positive indicator.

Why This Matters

Browser fingerprinting is used by advertising networks, fraud detection systems, and — as we have seen — even AI tools like Claude Code. Understanding what your browser reveals helps you make informed decisions about your online privacy. Our browser fingerprint scanner at fuck-claude.app gives you a concrete score showing exactly how identifiable your browser is in the context of China user detection.