Scan to join WeChat groupAre You a 「Claude China User」?
Nothing runs until you click. The scan happens entirely in your browser — zero upload.
Which signals we check
Six regional fingerprints, weighted into a 0–100 risk score.
Intl.DateTimeFormat reports the same system time zone Claude Code reads, matched against Asia/Shanghai, Asia/Urumqi and other China zones.
—+0Inspects navigator.languages; a zh-CN / Simplified Chinese primary scores highest.
—+0Uses canvas width probing to detect mainland Chinese fonts such as Microsoft YaHei and PingFang.
—+0The locale the browser uses for date / number formatting.
—+0Whether getTimezoneOffset() equals UTC+8.
—+0Inferred OS vendor from the UA — a weak related signal.
—+0How it works
When Claude Code points ANTHROPIC_BASE_URL at a relay, the operator can read the same system time zone your OS reports — and combine it with your browser language, Chinese fonts, Intl locale, UTC+8 offset and emoji vendor to guess whether you are a Chinese user.
A web page cannot read everything Claude Code can, but the key signals line up: this tool reads the very same system time zone, then stacks the other five fingerprints and weights them. A signal counts as matched at ratio ≥ 0.25; buckets are Low 0–30, Medium 31–60, High 61–100.
FAQ
Does Claude really check my time zone?expand_more
A relay operator can. Your OS time zone travels with many requests, and it is one of the strongest region tells — which is exactly why it carries the highest weight here.
Is this score Claude's real verdict?expand_more
No. This is a public, reverse-engineered estimate for fun and awareness. It only reflects browser-readable fingerprints, not any official Anthropic judgement.
How do I lower the score?expand_more
Switch your system time zone away from China zones, set a non-zh browser language, and reduce mainland-only fonts. But most of these also change your daily experience — decide what is worth it.
Do you upload my data?expand_more
No. Every check runs in your browser and nothing leaves your device. There is no detection request in the network tab.
All detection runs locally in your browser. The scan result never leaves your device, and the matched signals are never sent anywhere.