Timezone Leak Test
See the timezone, offset and daylight-saving profile your browser reports, and whether those three answers could all come from the same zone. Free, no signup, results stay on this page.
- Runs entirely in your browser
- Results are not uploaded
- No signup
See the timezone your browser is publishing
The check reads the IANA zone name your browser resolves, the offset your clock reports right now, and the offsets it produces in January and July — then asks whether all three could come from one real zone.
Runs entirely in this browser. Nothing is uploaded, nothing is stored, no signup.
Now give every account its own device.
A clean browser is still one browser. Sendwin runs each profile in isolation with its own fingerprint, cookies and proxy, so the accounts you work on never look like they came from the same machine.
- Isolated profiles, each with its own fingerprint and cookies
- A proxy per profile, with the timezone bound to the proxy country
- Windows, macOS and Linux — plus cloud sessions when you need them
The free plan includes 10 minutes of cloud browsing a day.
What your clock tells a website
Your browser publishes a named IANA timezone — Europe/Berlin, America/New_York — alongside a UTC offset it derives from the system clock. Any page can read both without asking. Fraud systems read them too, and then compare them with the country your connection appears to exit from, because the two are supposed to describe the same place. A German zone arriving on a US exit address is one of the cheapest and most reliable proxy tells there is.
This test reads the zone name, the current offset, and the offsets your clock reports in January and July, then checks whether all of them could come from one real zone. It is a local, mechanical check: no guessing which country you ought to be in. Where a comparison needs information only a server can see, the row says so rather than filling the gap with a third-party service.
Why timezone is the fastest proxy tell
The IP address tells a site where your connection exits. The timezone tells it what your machine believes the local time is. Both are free to read on the first page load, neither needs consent, and on an ordinary visitor they agree. When they disagree, the site does not have to prove anything — it simply scores an account that says it is in Berlin while its browser keeps time in Los Angeles. This is why changing the exit IP on its own rarely helps: the clock stays where the machine is, and the contradiction arrives with the very first request.
The zone name, the offset and the DST profile all have to agree
A named zone is more than a number. Europe/London is UTC+00:00 in January and UTC+01:00 in July, Asia/Tokyo never shifts at all, and southern-hemisphere zones move the opposite way. This test asks your clock for its offset in both months and compares that pair against what the named zone should produce. Patching one and not the other is what most naive timezone spoofing does: the JavaScript API returns the new zone while the underlying clock keeps the old offsets, or the daylight-saving transitions land on the wrong dates. Either way, the two answers cannot both be true.
Language and locale are separate settings
It is a common mistake to expect navigator.language and the timezone to line up. They come from different places: the language list follows your browser's language preferences, while the resolved Intl locale and zone follow the operating system's regional settings. An English-language browser in Warsaw is completely ordinary, and so is a French interface on a machine set to Europe/Lisbon. This check raises a soft note only when a pairing is unusual for the region, never a failure — travellers, expats and English-first interfaces are far too common for a language mismatch to mean much on its own.
What the check reads
- 1
Read what the browser reports
The check collects the resolved IANA zone name, the current UTC offset taken straight off the Date object, and the offsets your clock produces in January and July.
- 2
Check the zone against the clock
Those offsets are compared with the ones the named zone should produce, daylight-saving transitions included. A real machine derives both from the same zone database, so they match.
- 3
Compare against your exit country
The last row lines the browser zone up against the region your connection exits from. That comparison needs a server that can see your egress address, and it is not switched on yet — see the note below.
Other free checks
Your clock is one of several things a site expects to match your exit country. These cover the rest.
Timezone leak FAQ
Why a VPN never moves your clock, why changing the system time backfires, and which zone to run with a proxy.
It is when the timezone your browser reports contradicts where your connection appears to come from, or contradicts itself. The classic case is a proxy in one country and a system clock still set to another, so a site reads a US exit address next to a European zone. The mismatch is visible on the first page load, before you log in or type anything.
No, and it usually makes things worse. Sites read the named zone and the offset your operating system derives from it, not the time you display. Moving the clock forward two hours changes neither, so nothing this page measures moves: the zone name stays where it was and the offset comparison still agrees with it. What does break is everything that depends on the time being right — your clock now disagrees with every server you talk to, certificate validity windows get less reliable, and one-time codes stop matching. Change the zone, not the clock.
Because a VPN moves network traffic and nothing else. The timezone comes from your operating system's regional settings, which the tunnel never touches. That is exactly the gap this test exists to show: the exit address moved, the clock did not, and the two now describe different continents.
Because our own lookup service for it is not switched on yet. Comparing your zone against the region your connection exits from needs a server that can see your egress address, and we are not willing to hand your address to a third-party geolocation API to fill the row in the meantime. Until our endpoint is live, that row honestly reports that it could not be read. Every other check on this page is measured locally.
They should. A worker asks the same engine for the zone, so on an untouched browser the answer is identical. A shim that patches only the main-thread API is a well-known failure mode: the page reports the new zone while a worker keeps reporting the real one, and collecting both takes a site a couple of lines. If a timezone is going to change, it has to change where the engine reads it.
The one that belongs to the country your proxy exits from, including that zone's daylight-saving behaviour. Picking a nearby zone with the same current offset works until the transition dates diverge, and then it stops working in a way that is easy to score. Sendwin binds each profile's timezone to its proxy's country automatically, so the pairing stays correct without you tracking it per account.
No. Language preferences and regional settings are configured separately and legitimately differ — English interfaces are common everywhere. It is worth knowing that some systems still score the combination, so a zone and language that are plausible together attract less attention than an unusual pairing. But a language mismatch is not the same class of signal as a zone that contradicts your exit country.
Still have questions? Talk to us →
What this result covers
One honest limitation: the comparison against your exit country is not live on this page yet, because it needs a lookup service of our own and we will not route your address through a third-party geolocation API instead. Everything else here — the zone name, the offset and the daylight-saving profile — is measured in your browser and stands on its own. Read a clean result as “this browser's clock is internally consistent”, not as “my zone matches my IP”.
Let the timezone follow the proxy.
Sendwin binds each profile's timezone to its proxy country, so the clock and the exit address describe the same place without you tracking it per account. Free for 30 days on Windows, macOS and Linux.
30-day free trial · $0 today · cancel anytime — your profiles stay on your machine