svelte/documentation/docs/05-special-elements/07-svelte-options.md

title
<svelte:options>

<svelte:options option={value} />

The <svelte:options> element provides a place to specify per-component compiler options, which are detailed in the compiler section. The possible options are:

• runes={true} — forces a component into runes mode (see the Legacy APIs section)
• runes={false} — forces a component into legacy mode
• namespace="..." — the namespace where this component will be used, can be "html" (the default), "svg" or "mathml"
• customElement={...} — the options to use when compiling this component as a custom element. If a string is passed, it is used as the tag option
• css="injected" — the component will inject its styles inline: During server side rendering, it's injected as a <style> tag in the head, during client side rendering, it's loaded via JavaScript

[!LEGACY] Deprecated options Svelte 4 also included the following options. They are deprecated in Svelte 5 and non-functional in runes mode.

• immutable={true} — you never use mutable data, so the compiler can do simple referential equality checks to determine if values have changed
• immutable={false} — the default. Svelte will be more conservative about whether or not mutable objects have changed
• accessors={true} — adds getters and setters for the component's props
• accessors={false} — the default

<svelte:options customElement="my-custom-element" />