Posted over 2 years ago. Visible to the public. Repeats.

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

Some pseudo-elements need to be addressed with vendor prefixes. E.g. ::selection 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:

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::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:

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::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:

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=selection ::-moz-selection @content ::selection @content

Then use it like this in your .sass file:

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+selection 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).

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Henning Koch
Last edit:
3 months ago
by Besprechungs-PC
Keywords:
declaration
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