diff --git a/apps/svelte.dev/content/docs/svelte/02-runes/04-$effect.md b/apps/svelte.dev/content/docs/svelte/02-runes/04-$effect.md
index 3e71a3ab4..9485d6038 100644
--- a/apps/svelte.dev/content/docs/svelte/02-runes/04-$effect.md
+++ b/apps/svelte.dev/content/docs/svelte/02-runes/04-$effect.md
@@ -256,6 +256,30 @@ const destroy = $effect.root(() => {
destroy();
```
+## `$effect.allowed`
+
+The `$effect.allowed` rune is an advanced feature that indicates whether or not an effect or [async `$derived`](await-expressions) can be created in the current context. To improve performance and memory efficiency, effects and async deriveds can only be created when a root effect is active. Root effects are created during component setup, but they can also be programmatically created via `$effect.root`.
+
+```svelte
+
+
+
+```
+
## When not to use `$effect`
In general, `$effect` is best considered something of an escape hatch — useful for things like analytics and direct DOM manipulation — rather than a tool you should use frequently. In particular, avoid using it to synchronise state. Instead of this...
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