The markup for switches is <input type="checkbox" switch>. It comes built-in with ::thumb and ::track pseudo-elements. The ::before and ::after pseudo-elements can also be used for extra possibilities!
The switch control is enabled in Safari Technology Preview.
The native switch supports the accent-color and color-scheme CSS properties.
Your browser does not support the ::thumb and ::track pseudo-elements. The demos below will not render properly.
The pseudo-elements can be enabled in Safari Technology Preview behind the relevant feature flag in Develop > Feature Flags. See Apple's documentation on how to enable the develop menu if you don't yet have it enabled.