CSS: Don't target multiple vendor-prefixed pseudo-elements in a single rule

Some pseudo-elements Archive need to be addressed with vendor prefixes. E.g. ::selection Archive is not supported by Firefox, you need to use ::-moz-selection instead.

What you cannot do is to define a single CSS rule to address both the standard and vendor-prefixed form:

::selection, ::-moz-selection {
  background-color: red;

This rule will be ignored by all browsers. The reason is that if a browser does not know all pseudo elements in a selector, it ignores the entire rule. This is because the CSS spec says so.

So you need to copy & paste the rule instead:

::selection {
  background-color: red;

::-moz-selection {
  background-color: red;

If you're using a CSS preprocessor like Sass, you can write a mixin that does the copying and pasting for you:


Then use it like this in your .sass file:

  background-color: red

You will still have the rule twice in your CSS, but your .sass will be DRY (and the CSS will compress well before delivery).

Henning Koch over 5 years ago
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