Uwarp

Are you a Claude “China user”?

  • 100% local scan
  • Results never uploaded
  • Open source inspired
0/ 100

Ready to scan

What gets scanned

Six locale fingerprints, weighted to a 0–100 risk score.

  • System timezoneClaude sameWeight 30

    Intl.DateTimeFormat exposes the same OS timezone Claude Code reads; compared against Asia/Shanghai, Asia/Urumqi and other China zones.

  • Browser languageWeight 24

    navigator.languages — zh-CN / Simplified Chinese at the top of the list scores highest.

  • Installed Chinese fontsWeight 20

    Canvas width-probing for Simplified / Traditional Chinese fonts such as Microsoft YaHei and PingFang SC.

  • Intl localeWeight 10

    The locale your browser resolves for date and number formatting.

  • Timezone offsetWeight 8

    Whether getTimezoneOffset() equals UTC+8.

  • Emoji rendering styleWeight 8

    OS vendor guessed from the user agent; a weak, loosely correlated signal.

Help Us Improve

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Are you a Claude “China user”?

One-click check of your browser timezone, language, Chinese fonts and locale to see if Claude Code would flag you as a China user. 100% local, nothing uploaded.

What is the Claude China user check?

This hosted scanner replicates the Fuck Claude browser tool: it reads six locale fingerprints in your browser—system timezone, UI language, installed Chinese fonts, Intl locale, UTC+8 offset, and emoji style—and weights them into a 0–100 risk score. Only the system timezone maps directly onto Claude Code’s reported proxy fingerprinting; the rest are broader Chinese-environment signals. Everything runs locally in your browser with no uploads.

What gets scanned

Six weighted signals that mirror the open-source Fuck Claude detector.

  1. System timezone (30 pts): Intl.DateTimeFormat reads the same OS timezone Claude Code reportedly checks against Asia/Shanghai and Asia/Urumqi.
  2. Browser language (24 pts): navigator.languages — zh-CN or Simplified Chinese at the top scores highest.
  3. Installed Chinese fonts (20 pts): Canvas width-probing for Microsoft YaHei, PingFang SC, and other SC/TC fonts.
  4. Intl locale (10 pts): The locale your browser resolves for date and number formatting.
  5. Timezone offset (8 pts): Whether getTimezoneOffset() equals UTC+8.
  6. Emoji rendering style (8 pts): OS vendor guessed from user agent — a weak, loosely correlated signal.

How the check works

Understanding the score bands and what Claude Code reportedly reads.

  1. Start scan: Click Start scan to run an animated pass over all six signals. The gauge climbs as contributions add up.
  2. Read your band: Low 0–30, Medium 31–60, High 61–100. Signals scoring ≥0.25 count as hits.
  3. Focus on timezone: When Claude Code uses a non-official ANTHROPIC_BASE_URL endpoint, public reverse-engineering reports say it reads OS timezone and proxy hostname, encoding results into the system prompt via Unicode steganography.
  4. Treat as an estimate: Only timezone maps one-to-one onto Claude’s reported mechanism. Use the score for reference, not as an official verdict.

Frequently Asked Questions

Have questions? We have answers.

Inspired by the open-source Fuck Claude project. For reference only, based on public reverse-engineering reports — not an official statement or advice.

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