What it is
Your browser resolves an IANA zone such as Asia/Shanghai from the operating system. It shapes every Date object and every Intl formatter — and it is readable by any script.
How websites read it
Intl.DateTimeFormat().resolvedOptions().timeZone
// → "Asia/Shanghai" vs IP geolocation → "Asia/Singapore"The site also knows your IP. A geolocation database maps that IP to a zone. Two strings, one comparison.
Why it identifies you
A person browsing from Singapore has a Singapore clock. The zone changes rarely, so it is also a stable piece of identity.
How risk-control systems use it
Zone mismatch is the cheapest proxy check there is, which is why almost every anti-fraud vendor runs it. Some also compare the numeric UTC offset, so neighbouring zones with the same offset only earn a softer flag.
Common mistakes
Switching proxies without switching the zone; setting the zone but not the language; profiles that share one machine clock across ten countries.
Mango is accepting waitlist registrations. These capabilities describe its first release; client access opens with invitations.
How Mango Browser handles it
CustomModes: follow the proxy exit IP (default) or set a fixed zone. Date, Intl and the offset all report the same zone.
Check yours
Jump to this signal in your scan results.