Let’s use (X, X, X, X) for talking about specificity

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Chris Coyier on

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I was just chatting with Eric Meyer the other day and I remembered an Eric Meyer story from my formative years. I wrote a blog post about CSS specificity, and Eric took the time to point out the misleading nature of it (I remember scurrying to update it). What was so misleading? The way I was portraying specificity as a base-10 number system.

Say you select an element with ul.nav. I insinuated in the post that the specificity of that selector was 0011 (eleven, essentially), which is a number in a base-10 system. So I was saying tags = 0, classes = 10, IDs = 100, and a style attribute = 1000. If specificity was calculated in a base-10 number system like that, a selector like ul.nav.nav.nav.nav.nav.nav.nav.nav.nav.nav.nav (11 class names) would have a specificity of 0111, which would be the same as ul#nav.top. That’s not true. The reality is that it would be (0, 0, 11, 1) vs. (0, 1, 0, 1) with the latter easily winning.

That comma-separated syntax like I just used solves two problems:

  1. It doesn’t insinuate a base-10 number system (or any number system)
  2. It has a distinct and readable look

I like the (X, X, X, X) look. I could see limiting it to (X, X, X) since a style attribute isn’t exactly a selector and usually isn’t talked about in the same kind of conversations. The parens make it more clear to me, but I could also see a X-X-X (dash-separated) syntax that wouldn’t need them, or a (X / X / X) syntax that probably would benefit from the parens.

Selectors Level 3 uses dashes briefly. Level 2 used both dashes and commas in different places.

Anyway, apparently I get the bug to mention this every half-decade or so.