Mix and relative color
Type any color-mix(), relative color (oklch(from ...)), or light-dark() expression. resolve evaluates it in the library. The page also assigns the same text to an element and reads back the browser’s computed color, so the right-hand panel is your browser’s own answer. The comparison is the ΔEOK between the two in OKLab.
color-map
This browser
If your browser does not support an expression, such as relative color in an older release, the right panel says so and no comparison is made. A larger difference on a wide-gamut color is expected: browsers clip to the display when they compute a color, and the library returns the exact value.