The :has() pseudo-class lets you style an element based on its descendants. article:has(img) targets articles that contain an image. label:has(input:checked) styles a label when its child checkbox is ticked.
Browser support landed across Chrome, Safari, and Firefox in 2023. It removes many cases where you would have reached for a JavaScript class toggle.
It is a powerful selector — use it sparingly in performance-critical selectors. Browsers optimise it well, but a massive query selector with deeply nested :has() can still cost layout time.