::part
A selector used inside a Shadow DOM that allows you to style specific internal pieces of a web component from the outside (the 'global' CSS).
Quick example
my-custom-component::part(button) {
/* Styles the 'button' part exposed by the web component's shadow tree */
background: var(--brand-color);
border-radius: 8px;
}::part Browser Support
Widely available Since 2020 95% 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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