IP, Timezone and Language Check

Why sites compare these

Your IP address gives a site an approximate location before any page loads. The browser then reports its own view of where you are. Scripts read the time zone name through the Intl API (resolvedOptions) and the current offset through Date. The browser states its preferred languages twice: in the Accept-Language request header defined in RFC 9110, and in navigator.languages.

Each value is cheap to read and easy to leave out of step. A VPN or proxy changes the IP and nothing else, so a laptop set to New York time that exits in Berlin reports America/New_York with a German address. Risk systems compare the two because that pattern is common in automated and multi-account traffic. Travellers, expats and people who keep a device on home time produce the same pattern for ordinary reasons, which is why a mismatch usually leads to an extra check rather than a block on its own.

Research on evasive bots points the same way. A 2024 study that sent traffic from 20 bot services to a site protected by two anti-bot services found that bots changing their fingerprints often left attributes that contradicted each other, and that rules looking for those contradictions cut the bots' evasion rate by close to half (Venugopalan et al., FP-Inconsistent). Agreement between values matters more than any single value.

What each row compares

• Time zone. The IANA zone name your browser reports through Intl, against the zone our hosting edge assigns to your IP. Two different names that keep the same offset all year, such as Europe/Berlin and Europe/Paris, count as a match.
• UTC offset now. How many hours and minutes your browser is ahead of or behind UTC at this moment, against the same figure for the IP's zone. This is the number most scripts compare.
• Clock agrees with zone. The offset from Date against the offset of the Intl zone. Both come from the same browser, so a difference means only one of them was overridden.
• Languages and country. Whether your browser's languages include one that is official or widely used in the IP country, from a table of about a hundred countries. Countries outside the table are not assessed.
• Header and browser languages. The Accept-Language header our server received, against navigator.languages read by the page.

How to fix a mismatch

Decide which side should move. The IP is usually chosen for a reason, so change the browser to match it.

• Antidetect browser profile. Most profiles have time zone, language and geolocation settings with an option to fill them from the proxy's IP. Assign the proxy first, then start the profile so the values come from the proxy exit, and run this check inside the profile rather than in your everyday browser. The antidetect browser guide and the setup guides cover the settings tool by tool.
• Operating system. On Windows, open Settings, Time and language, Date and time, turn off the automatic time zone and choose one. On macOS, open System Settings, General, Date and Time. The browser follows the system zone.
• Browser languages. In Chrome, open Settings, Languages; in Firefox, Settings, General, Language, where you choose the languages for displaying pages. Put the language you want first. The Accept-Language header and navigator.languages follow that order.
• Countries with several zones. For the United States, Canada, Australia, Brazil or Indonesia, match the zone this check shows for your IP rather than the capital's.

For browser automation, set the zone and locale on the context that uses the proxy. In Playwright:

const context = await browser.newContext({
  proxy: { server: 'http://HOST:PORT', username: 'USER', password: 'PASS' },
  timezoneId: 'Europe/Berlin',
  locale: 'de-DE',
});

Puppeteer has page.emulateTimezone() for the zone, and page.setExtraHTTPHeaders() can send a matching Accept-Language header. After any change, run the check again from the same session.

Limits of IP geolocation

IP location is an estimate from a database, not a measurement. The location in this check comes from our hosting provider's edge, which attaches the country, region, city and time zone to each request (Vercel request headers). Other sites license other databases and can place the same address somewhere else. Network operators can publish where their ranges are used through geofeeds (RFC 8805), and databases that read those feeds agree with each other more often.

Mobile addresses are the hardest case. A phone's traffic leaves the carrier's network through a regional gateway, so its address often geolocates to the gateway's city, or only to the country, wherever the phone actually is. For a mobile proxy, match the country and the zone this check reports and do not expect agreement at city level. Coronium sells lines by country and carrier; mobile proxy locations shows what is in stock.

Daylight saving is a seasonal trap. Two zones can share an offset today and differ next month, as Europe/London and Africa/Abidjan do in winter. The check compares offsets now and half a year ahead and tells you when the agreement is only seasonal. Zone names and their rules come from the IANA time zone database.