diff --git a/documentation/docs/98-reference/21-svelte-legacy.md b/documentation/docs/98-reference/21-svelte-legacy.md
index 73cbea16cd..f313baca0b 100644
--- a/documentation/docs/98-reference/21-svelte-legacy.md
+++ b/documentation/docs/98-reference/21-svelte-legacy.md
@@ -2,4 +2,6 @@
 title: svelte/legacy
 ---
 
+This module provides various functions for use during the migration, since some features can't be replaced one to one with new features. All imports are marked as deprecated and should be migrated away from over time.
+
 > MODULE: svelte/legacy
diff --git a/documentation/docs/98-reference/21-svelte-reactivity.md b/documentation/docs/98-reference/21-svelte-reactivity.md
index 0d2768dd8d..6857c1dba8 100644
--- a/documentation/docs/98-reference/21-svelte-reactivity.md
+++ b/documentation/docs/98-reference/21-svelte-reactivity.md
@@ -2,4 +2,24 @@
 title: svelte/reactivity
 ---
 
+Svelte provides reactive versions of various built-ins like `SvelteMap`, `SvelteSet` and `SvelteURL`. These can be imported from `svelte/reactivity` and used just like their native counterparts.
+
+```svelte
+<script>
+	import { SvelteURL } from 'svelte/reactivity';
+
+	const url = new SvelteURL('https://example.com/path');
+</script>
+
+<!-- changes to these... -->
+<input bind:value={url.protocol} />
+<input bind:value={url.hostname} />
+<input bind:value={url.pathname} />
+
+<hr />
+
+<!-- will update `href` and vice versa -->
+<input bind:value={url.href} />
+```
+
 > MODULE: svelte/reactivity