:where() has a cool specificity trick, too.

:is() and :where() are CSS pseudo-selectors offering similar functionality but differing significantly in specificity. Recently, :is() has gained popularity due to broader browser support, simplifying complex selectors. However, :where() provides a crucial advantage in controlling specificity.

:is() inherits the specificity of its most specific argument. This can be advantageous for increasing specificity without adding extra classes, as demonstrated:

:is(.button, #increase#specificity) {
  /* Specificity increases */
}

Conversely, :where() always has zero specificity, regardless of its arguments. This is particularly useful for lowering specificity in situations where a higher-specificity selector might unintentionally override a more general style. Consider this example:

.card :is(.title, p) { /* High specificity due to .title */
  color: red;
}

.card p { /* Lower specificity */
  color: yellow;
}

Here, red wins due to :is()'s inherited specificity. Switching to :where() changes the outcome:

.card :where(.title, p) { /* Zero specificity */
  color: red;
}

.card p { /* Lower specificity, but still wins */
  color: yellow;
}

Now, yellow prevails because :where()'s specificity is lower.

Choosing between :is() and :where() depends on your specific needs. Generally, starting with :is() is recommended for its simplicity. However, if you encounter specificity conflicts, :where() offers a powerful tool to manage and reduce specificity, preventing unintended style overrides. While low specificity is generally preferred for maintainability, the extreme zero specificity of :where() might introduce its own complexities. Therefore, a balanced approach is key – use :is() unless you need the precise specificity control offered by :where().

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