svelte/documentation/docs/02-runes/01-what-are-runes.md

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What are runes?

[!NOTE] rune /ro͞on/ noun

A letter or mark used as a mystical or magic symbol.

Runes are symbols that you use in .svelte and .svelte.js/.svelte.ts files to control the Svelte compiler. If you think of Svelte as a language, runes are part of the syntax — they are keywords.

Runes have a $ prefix and look like functions:

let message = $state('hello');

They differ from normal JavaScript functions in important ways, however:

• You don't need to import them — they are part of the language
• They're not values — you can't assign them to a variable or pass them as arguments to a function
• Just like JavaScript keywords, they are only valid in certain positions (the compiler will help you if you put them in the wrong place)

[!LEGACY] Runes didn't exist prior to Svelte 5.