Why Does `input:not(:empty)` Never Match Any Element?

Understanding the :not(:empty) CSS Selector

The :not() selector negates the match criteria specified within its parentheses. When applied to the :empty pseudo-class, the :not(:empty) selector should target elements that are not empty. However, users have encountered difficulties using this combination.

The Void Element Issue

The element is a void element, meaning it does not have any content. According to the HTML definition of "empty," void elements are always considered empty. This means that they will always match the :empty pseudo-class, regardless of whether they have a value.

Selector Spec Implications

The Selectors specification further clarifies that the :empty pseudo-class matches elements with no child nodes or content nodes with non-zero length. As such, the combination of input:not(:empty) will never match any element in a valid HTML document.

Alternative Solutions

Styling empty fields dynamically using CSS alone may be challenging. However, it is possible to select initially empty fields that lack a value attribute (input[value=""]) or have an empty value attribute (input:not([value])). Beyond these options, alternative methods may be necessary to address the styling of empty fields.

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