Uses navigator.platform.startsWith('Mac'). navigator.platform is
formally deprecated in favor of navigator.userAgentData, but it remains
universally available and is honest about the OS string ("MacIntel",
"MacPPC", "iPhone" → starts with "Mac" only on desktop macOS). If/when we
adopt navigator.userAgentData, update this one function.
Returns false in non-browser contexts (e.g., Node test runners) so
default-derivation code paths remain deterministic outside the browser.
Whether the current browser is running on macOS.
Uses
navigator.platform.startsWith('Mac').navigator.platformis formally deprecated in favor ofnavigator.userAgentData, but it remains universally available and is honest about the OS string ("MacIntel", "MacPPC", "iPhone" → starts with "Mac" only on desktop macOS). If/when we adoptnavigator.userAgentData, update this one function.Returns
falsein non-browser contexts (e.g., Node test runners) so default-derivation code paths remain deterministic outside the browser.