This hint serves solely as a backwards compatible shim for sites relying on "WoW64-ness" (32-bit app running in 64-bit Windows) as they transition from the User-Agent string to UA-CH. It returns a boolean value.


We would like to provide a seamless transition from User-Agent-based use cases to UA-CH. The "WoW64" bit is the last piece, and is largely included for backwards compatibility rather than trying to design an API that exposes future binary and OS bitness differences.


Specification link

Specification being incubated in a Community Group

Status in Chromium


Proposed (tracking bug)

Consensus & Standardization

After a feature ships in Chrome, the values listed here are not guaranteed to be up to date.

  • No signal
  • No signal
  • Mixed signals


Intent to Prototype url

Intent to Prototype thread

Search tags

wow, wow64, ua-ch, uach,

Last updated on 2022-04-25