Claude Network Environment Check

Claude connectivity and network egress checks

• Claude domain egress check：Checks of egress to claude.com or claude.ai are not implemented. This page only shows connection information observable when visiting IPVeya; it does not send requests to those domains or compare their network paths. If implemented in the future, results would describe only observations from that browser request, not account status or an official risk decision.
• WebRTC address check：This page checks public candidates visible through browser WebRTC and compares them locally with the egress IP seen when visiting IPVeya. If a different public address is found, review WebRTC and proxy/VPN routing; the difference alone does not prove traffic bypassed a proxy.
• DNS resolution path check：When configured, the browser resolves a one-time random hostname and checks Cloudflare DNS Analytics for the recursive resolver source address. This may differ from the DNS configured on the device; missing or delayed records remain unknown and do not establish whether a leak exists.

Browser environment signals

The following settings and rendering traits are observable to the browser. They are informational and cannot on their own establish identity, location, or a platform decision.

• Language preference: Reads the browser's exposed language list, such as zh-CN or zh, and displays the current language settings.
• Time zone: Reads the system time zone and UTC offset exposed by the browser, such as Asia/Shanghai. This reflects device settings and does not establish the user's location.
• Emoji rendering differences: Canvas can optionally be used to observe Emoji rendering differences. Results vary by operating system and browser and cannot accurately identify a region.
• Fonts and rendering traits: When permitted by the browser, observes font candidates and text-rendering differences. Font availability alone does not establish location or identity.

These local signals are processed temporarily only after the user starts a check. They are not sent to the IPVeya API or stored.

Possible Claude Code detection mechanisms

According to the latest reverse security research, the risk control mechanism in Anthropic’s desktop tool, Claude Code, is highly covert. No matter how perfectly you disguise your network connection, it will secretly transmit your time zone and proxy status to Anthropic’s servers in the background by subtly adjusting the time format and punctuation in system prompts.

• Proxy or relay checks: One hypothesis is that Claude Code may read system proxy settings or relay hostnames and match specific keywords; the mechanism and rules have not been verified.
• Time-zone checks: One hypothesis is that it may read system time zones such as Asia/Shanghai or Asia/Urumqi; there is insufficient evidence that this is used for risk decisions.
• Date-format or Unicode punctuation changes: One unverified hypothesis is that punctuation changes in date strings could encode environment signals—for example, replacing a date hyphen (-) with a slash (/), or replacing an ASCII apostrophe (') with ’, ʼ, or ʹ.

Until publicly verifiable source research, reproducible steps, or an official Anthropic statement is available, these hypotheses should not be presented as fact or as evidence that Claude Code covertly transmits user information.

Network and device environment settings

If a check shows an unexpected result, first review whether your device settings and network routes match your actual needs. The following adjustments cannot guarantee approval by Claude or another platform, and they do not indicate account risk.

• Review the system time zone: Check that the device time zone matches your actual location. The setting changes only the device's clock; it does not change the IP address or network egress, or establish a person's location.
• Review proxy and network routing: Check whether command-line tools use the proxy or VPN route you expect. TUN mode or a software router may change traffic forwarding, depending on the configuration. Use a connection test to confirm the actual egress; do not assume this hides relay or proxy information.

Claude Code community report

A community static reverse-engineering report on the Claude Code v2.1.169 Windows binary claims that the configured endpoint hostname and certain system time zones affect the Unicode apostrophe and date separator in a system-prompt date line. The report does not establish intent and is not an official Anthropic statement; it cannot establish behavior in other versions or Claude on the web.

IPVeya does not read ANTHROPIC_BASE_URL, proxy hostnames, or system prompts. The experimental score uses Intl locale and UTC+8 as low-weight local signals, but they are not verified Claude Code detection signals. Browser and device categories are temporarily classified on this device and are not sent to the IPVeya API.

Source: Claude Code community reverse-engineering report (not official confirmation)

What IPVeya checks

• Network exit: Shows the current request IP, available location and ASN, and network signals actually returned by the configured provider. It does not connect to Claude domains to measure their network exits.
• Browser and system: After the check starts, browser language, system time zone, Intl locale, and UTC offset are read locally; font candidates, browser category, device category, and Emoji rendering are also observed temporarily.
• WebRTC: Contacts Cloudflare STUN; candidates are compared with the current egress IP on this device only. The STUN service may see your public egress IP.
• DNS: When configured, observes the recursive resolver source address for a random query; it is not direct proof of the device-configured DNS and does not by itself determine a leak.

Experimental score and prompt

The experiment references ten signal weights proposed by the community: system time zone 24, browser language 18, Chinese fonts 14, vendor fonts 10, WebRTC 10, Chinese browser 8, device brand 6, Intl locale 4, UTC offset 3, and Emoji style 3. These are uncalibrated community hypotheses, not Anthropic rules.

Related signals have per-category contribution caps. Only observed items count toward the score and coverage; unknown, failed, unsupported, and untested items are not treated as non-matches. A band is shown only when coverage reaches 70%: 0–24 lower, 25–49 moderate, and 50–100 higher. The egress-region prompt is separate from the score and is not an account, identity, or platform risk decision.

Privacy and source checks

• WebRTC / STUN: A STUN service can see the request's public source IP address and port and return a public candidate. This page compares the candidate with the current egress IP locally and does not send the candidate address to the IPVeya API. The STUN operator's own policies govern how it handles requests.
• Browser extensions: In Chrome, open chrome://extensions to review extension permissions and site access. Remove extensions you no longer use or trust; where available, limit site access to specific sites or on-click access.
• Service region policy: Anthropic supported regions policy. IPVeya's network location information does not replace the official policy or determine account eligibility.