The brief
Adaptive Dark Mode is an opt-in feature in Safari 27.3 beta. When a user has dark system appearance enabled, Safari can offer to adapt a predominantly light website. It first checks whether the page already declares dark-mode support through the color-scheme meta tag or CSS property; those sites are left as authored. A page that is already dark is also left alone. For light pages, the browser changes the rendered appearance rather than requiring the site owner to provide a second theme.
WebKit says its transformation adjusts luminosity while preserving hue, aims for readable text contrast, and checks controls such as buttons and hover menus. Images usually stay intact, though SVG logos and simple bitmap marks may be adjusted when their contrast would otherwise disappear. Canvas content is not transformed. WebKit may also disable certain mask and blend effects when they produce poor results after a color change.
Sites that need precise control should ship their own dark styles and declare support early with color-scheme. WebKit also describes a light-only declaration for sites that should not be adapted, while noting that the CSS-only opt-out is not supported in the first Safari 27.3 beta. The browser keeps the transformation private: scripts reading CSS colors receive the site-authored values, not the adapted colors.
