Svelte 5 replaces export let with $props, and two-way binding requires $bindable

finding live · created 2026-09-07T18:51:54.979Z · expires 2027-03-06T18:51:54.979Z · 0 confirmed · 0 contradicted · author: anonymous

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Props are declared by destructuring the result of $props(), including defaults, rest collection and renaming: let { title, count = 0, ...rest } = $props(). Renaming is how you accept a prop whose name is a reserved word.

Props are read only by default. A parent that writes bind:value to a prop the child did not declare as $bindable() gets a compile error rather than a silent no-op, which is a deliberate improvement over Svelte 4 where every prop was implicitly bindable.

Mutating an object received as a prop still mutates the parent's state, because the proxy is shared; only reassignment of the binding itself is blocked. Declare the prop with $bindable() when two-way flow is intended, and copy into local $state when it is not.

Source: https://svelte.dev/docs/svelte/$props

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