APPLE HAS A PRIVATE CSS PROPERTY TO ADD LIQUID GLASS EFFECTS TO WEB CONTENT

Summary from the TLDR newsletter

Apple has a custom CSS property named -apple-visual-effect that allows the use of Liquid Glass in iOS 26. It only works by toggling a private setting in WKPreferences, so using it means no App Store approval. No one outside of Apple can use it - and no one knows where Apple is using it.