Imagine you put a link in your WordPress post, for example to https://green.example. You also set a link to https://red.example and to https://yellow.example. I would like to make it such that depending on the target URL of a link, a CSS class is automatically assigned to the link.

For example https://green.example should be assigned the class "green", https://red.example the class "red" and so on.

It should be definable for which links these classes should be assigned, not only for exact URLs (like https://green.example/example/hello.php), but also by rules like "for all URLs starting with https://green.example*".

Does anyone know how this can be done in a performance-saving way? Is JavaScript mandatory or can it be done with a WordPress function?

This function should ideally apply to all links, so not only within a post, but also if you use, for example, additional fields through ACF (Advanced Custom Fields).

1 Answer 1


This can be done with CSS 3 selectors. You can apply styles when an attribute starts with a value. ^= means "starts with" here.


Here is a demonstration.

This technique has excellent browser support. 99.78% of users will be able to see it in their browsers.

  • Wow, this is an incredibly elegant way. I didn't expect it to be possible simply through CSS. I thought you would have to implement it with javascript or via functions.php. That's awesome :-) Thanks!
    – dajana.s
    Sep 3, 2022 at 22:25

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