Comment by jeroenhd
MDN doesn't even have it yet. Looks like it's WebKit exclusive for a while.
The [draft for addition to the CSS spec](https://drafts.csswg.org/css-color-5/#resolving-contrast) just got added. Kind of wonder why Apple includes this in Safari as color-contrast rather than -webkit-color-contrast until other browsers have at least indicated a position on this draft. All I can find is decisions to defer the specifications (going back to as far as 2020).
Prefixes are no longer used for new features, and any that still exist are old. What happens now is that features are gated behind feature flags for testing until the browser working group settles on the final spec for that feature, at which point any browser-maker is free to implement it in public releases.