oj_windows is a fork of Oj (https://github.com/ohler55/oj) by Peter Ohler, adapted to build with the MSVC (mswin) Ruby toolchain: pthread mutexes replaced with Windows primitives, POSIX headers guarded, and SIMD string scanning enabled under MSVC. It provides the full Oj API (module Oj) and JSON-gem compatibility. Because it defines the same Oj module, it is a replacement for - and cannot be installed alongside - the upstream oj gem. Requires Ruby 3.4+ built with the MSVC toolchain (RubyInstaller/MinGW users should use the upstream oj gem instead).