svelte/documentation/docs/04-styling/01-scoped-styles.md

title
Scoped styles

Svelte components can include a <style> element containing CSS that belongs to the component. This CSS is scoped by default, meaning that styles will not apply to any elements on the page outside the component in question.

This works by adding a class to affected elements, which is based on a hash of the component styles (e.g. svelte-123xyz).

<style>
	p {
		/* this will only affect <p> elements in this component */
		color: burlywood;
	}
</style>

Specificity

Each scoped selector receives a specificity increase of 0-1-0, as a result of the scoping class (e.g. .svelte-123xyz) being added to the selector. This means that (for example) a p selector defined in a component will take precedence over a p selector defined in a global stylesheet, even if the global stylesheet is loaded later.

In some cases, the scoping class must be added to a selector multiple times, but after the first occurrence it is added with :where(.svelte-xyz123) in order to not increase specificity further.

Scoped keyframes

If a component defines @keyframes, the name is scoped to the component using the same hashing approach. Any animation rules in the component will be similarly adjusted:

<style>
	.bouncy {
		animation: bounce 10s;
	}

	/* these keyframes are only accessible inside this component */
	@keyframes bounce {
		/* ... *.
	}
</style>