The universal selector has the potential to be slower than other selectors in naïve CSS engines because CSS works by matching selectors from the right to the le

The universal selector has the potential to be slower than other selectors in naïve CSS engines because CSS works by matching selectors from the right to the left. A rule like `.baz *` matches every element on the page (vs something like `.baz .foo` which only matches elements with `.foo`). The match is only rejected after walking up the DOM tree to the root node to see if any parent elements have the `.baz` class or not. In the case of a single universal selector, there is no performance issue, the selector just matches every element, which is fine. In modern engines, there is also no performance issue, they JIT compile selectors[0] and do other stuff to be fast. Even old engines wouldn’t really have a performance issue in practice unless you were doing something else bad, like having extremely deep DOM trees with extremely large numbers of elements. [0] https://webkit.org/blog/3271/webkit-css-selector-jit-compiler/ https://webkit.org/blog/3271/webkit-css-selector-jit-compile...