:default
A pseudo-class that targets form elements (like buttons or checkboxes) that are the default among a set of similar elements.
Quick example
button:default {
/* Highlights the primary/default button in a form */
outline: 2px solid #3b82f6;
font-weight: bold;
}:default Browser Support
Widely available Since 2020 96% global usage
This feature is well established and works across many devices and browser versions. It has been available across browsers since 2020.
Safe to use without fallbacks.
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