Is there a difference in CSS selectors `:enabled` vs `not(:disabled)`

Question

Is there a difference in behaviour or browser support for using the CSS3 selectors :enabled or not(:disabled)?

I expect them to be functionally identical, and as they are both CSS3 selectors, browser support should be identical too.

Answer 1

Yes, there is a difference — :not(:disabled) can match elements that are neither :enabled nor :disabled. These are elements where enabled/disabled semantics simply don't apply, such as div, p, ul, etc.

The spec confirms this:

What constitutes an enabled state, a disabled state, and a user interface element is language-dependent. In a typical document most elements will be neither :enabled nor :disabled.

Interestingly, the same can't be said for :checked — there is no corresponding :unchecked pseudo-class, despite the fact that not all elements have checked/unchecked semantics either. See my answer to this question.

If you're qualifying these pseudo-classes with a type selector (such as input, select or textarea) or a class selector, you probably don't have to worry about this. Still, it makes more sense to use :enabled than :not(:disabled).

Browser support for the majority of level 3 pseudo-classes is indeed identical — there are no known browsers that support either :enabled or :disabled only. However, according to MDN it looks like Opera 9.0 and Safari 3.1 don't support :not(), although they do support :enabled and :disabled, and some other features like substring-matching attribute selectors and the general sibling combinator ~ are supported in IE7 with some issues and a little bit better in IE8.