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SpeedIQ

Timezone Leak Test

By Vathanakone Prakosay · Updated on · 4 min read

In short

This timezone leak test compares the time zone of your browser with the time zone of your public IP address. A VPN changes your IP, but not the clock of your device. If the two do not match, websites can see that you are probably not where your VPN server is.

Timezone leak testruns in your browser

Your browser time zone is read locally. To compare it, the test asks ipinfo.io ↗ for the time zone of your public IP address. Nothing runs until you click. Results stay in your browser; we do not store or receive them. Checks marked ↗ send one request to a third party (see Privacy, section 3.3).

    How does this timezone leak test work?

    The test reads two time zones and compares their UTC offsets.

    1. Your browser reports its time zone with JavaScript, as an IANA name such as Europe/Berlin (MDN, 2026; IANA, 2026). Every website can read it without asking.
    2. ipinfo.io returns the time zone of your public IP address. With a VPN, that is the location of the VPN server.
    3. The test compares the current UTC offsets. Different offsets mean a time zone mismatch.

    How do I read the result?

    A match means your time zone does not contradict your IP. A mismatch means it does.

    ResultWhat it means
    Same UTC offsetNo timezone leak. Your browser's timezone fits the location of your IP.
    Different UTC offsetTimezone leak: websites can see that your device clock and your VPN IP point to different regions.
    Browser reports UTCTor Browser and Firefox with Resist Fingerprinting report UTC on purpose (Tor Project, 2019; Mozilla, 2026).

    What is a timezone leak?

    A timezone leak is a mismatch between the time zone your browser reports and the location of your IP address. Your browser shares its time zone through JavaScript APIs such as Intl.DateTimeFormat and Date.getTimezoneOffset (MDN, 2026). A VPN changes your IP address, but the browser still uses the time zone of your operating system. A site that compares both can tell that the VPN location is probably not your real location.

    A timezone leak does not reveal your IP address. It reveals your region. Together with your language settings and the Accept-Language header, it can narrow down where you are, and it becomes part of your browser fingerprint.

    Does a VPN change my time zone?

    No. A VPN changes the route of your traffic and the IP address websites see. It does not change your system clock or the time zone setting of your device. Some VPN apps and browser extensions offer a time zone option; check it with this test.

    How do I fix a timezone leak?

    Make the two time zones match, or make the browser report a neutral value.

    Run the timezone leak test again after each change.

    Is a time zone mismatch always a problem?

    No. Travellers, remote workers and many VPN users have a mismatch for normal reasons. It matters if you want a website to believe you are in the VPN server's country, or if you want to keep your region private.

    What can this test not see?

    It sees only this browser. Other signals, such as a DNS leak or a WebRTC leak, can reveal more than your time zone. Check them with the VPN leak test and the WebRTC leak test, and read the geolocation privacy guide to see how websites estimate your location.

    FAQ

    Can websites see my time zone?

    Yes. Any website can read your browser time zone and UTC offset with JavaScript, without asking for permission.

    Does a VPN hide my time zone?

    No. A VPN changes your IP address but not your device clock. Your browser still reports the time zone of your operating system.

    How do I change the time zone my browser reports?

    Change the time zone of your operating system, or use Tor Browser or Firefox with Resist Fingerprinting, which report UTC.

    How do I know if my VPN is leaking?

    A time zone mismatch is a hint, not an IP leak. To check for IP, IPv6 and WebRTC leaks, run the VPN leak test.

    Does SpeedIQ store my time zone?

    No. The browser time zone is read locally. Only the request to ipinfo.io leaves your browser, and SpeedIQ stores nothing.

    More checks on SpeedIQ

    Sources