ith the introduction of Dark Mode in macOS Mojave last year, web developers have been asking for support in Safari to style web content that matches the system appearance. With the Safari 12.1 update in macOS 10.14.4, dark mode support in WebKit has arrived.Dark Mode Behaviors
By default there are no behavior changes with how pages look when a user is in dark mode. This preserves the standard assumptions web designers have had for almost thirty years — that a page defaults to a white background and black text. To change these defaults in dark mode would be a web compatibility nightmare.
However, this leaves a large area of the screen with potentially bright content in dark mode. For simple content, an app could transform colors in the document for dark mode. This is what Mail does in macOS Mojave — it displays simple email messages with a dark mode interpretation.
Not all web content is simple. For this reason Safari and WebKit do not auto-darken web content — documents will need to opt-in to dark mode. The main way to signal that your content supports dark mode it to adopt the new color-scheme style proper