Methodology

How Claude China User Detection Signals Work

SignalCheck Local combines nine browser-visible clues into a transparent 100-point estimate. These are the signals this independent tool checks; they are not a claim about signals used by Claude or Anthropic.

What the score can—and cannot—tell you

The score answers a narrow question: does this browser expose a collection of settings that commonly appears in a mainland China environment? It cannot inspect a Claude account, know an IP-based platform decision, read login history, or predict enforcement. A high score means several local clues agree; a low score means fewer clues matched.

Every detector runs in the browser. Signal values and results remain in page memory and are not sent with analytics events. If a browser blocks a capability, the corresponding signal is marked unavailable and contributes zero points instead of being guessed.

System timezone

26 points

The strongest signal checks the IANA timezone reported by the browser. Asia/Shanghai and recognized mainland China aliases add weight, but a timezone can be changed manually and does not prove physical location.

Browser languages

20 points

Primary Simplified Chinese preferences receive more weight than a secondary zh-CN preference. Invalid language tags are ignored so malformed browser data cannot create a positive match.

Common Chinese fonts

16 points

Canvas text widths are compared against generic fallback fonts to estimate whether common Chinese fonts are available. The page never reads font files, and privacy protections can make this check unavailable.

Vendor Chinese fonts

10 points

Fonts associated with device ecosystems, including MiSans and HarmonyOS Sans, provide a moderate clue. Installing a font is not evidence of nationality, residence, or account ownership.

Browser or WebView identifiers

8 points

Public browser brands and user-agent text are checked for identifiers associated with Chinese browsers or embedded app containers. Modern browsers may reduce or remove this information.

Device brand

6 points

When available, public client hints and conservative user-agent fallbacks can expose a model or vendor name. Desktop browsers and privacy-focused browsers often provide no useful model.

Intl locale

6 points

The locale resolved by the browser's internationalization API is checked for Simplified Chinese and mainland China regional preferences. Traditional Chinese regions are not treated as mainland matches.

UTC+8 offset

4 points

The current timezone offset adds weak supporting evidence. Many regions share UTC+8, so this signal is deliberately weighted far below the named timezone.

System and emoji proxy

4 points

Public operating-system text is used as a conservative proxy for system rendering traits. It is intentionally weak and becomes unavailable when the browser withholds the required information.

Check your current browser

Run the local scan, review every matched signal, and read the result as an estimate rather than an account verdict.

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