Svelte 5 runes

The core runes you use day to day.

$state

function

let v = $state(initial)

Creates deeply reactive state.

Prop	Type	Required	Description
`initial`	`T`	Yes	Initial value.

function

let v = $derived(expr)

A read-only value recomputed from other state.

Prop	Type	Required	Description
`expr`	`T`	Yes	Pure expression.

function

$effect(() => { ... })

Runs a side effect after the DOM updates; return a cleanup fn.

function

let { a, b } = $props()

Reads the component props.

function

let { v = $bindable(d) } = $props()

Marks a prop as two-way bindable.

Prop	Type	Required	Description
`d`	`T`	—	Default value.