Routing Concepts

Flat Mode or Tree Mode

When defining routes, you can choose between two organizational structures: flat or tree. Flat mode defines all routes at the router's root level, while tree mode organizes routes in a hierarchical structure.

router.ts

// Flat Mode
'/about': About,
'/about/work': Work,
'/about/work/mywork': MyWork,
'/about/contact': Contact,

// Tree Mode
'/about': {
  '/': About,
  '/work': {
    '/': Work,
    '/mywork': MyWork,
  },
  '/contact': Contact,
},

You can effectively combine both modes within the same router configuration for maximum flexibility.

Dynamic Routes

To create dynamic routes that match variable segments, prefix a route segment with a colon :. This allows that segment to match any value.

Multiple dynamic segments can be included in a single route:

'/user/:id': User,
'/user/:id/post/:postId': Post,

Access these dynamic segments in your components using the route.params object:

Post.svelte

<script lang="ts">
	import { route } from '../router';

	// Typed as { id?: string, postId?: string }
	route.params;
</script>

<main>
	<h1>Post</h1>
	<p>User ID: {route.params.id}</p>
	<p>Post ID: {route.params.postId}</p>
</main>

Catch-All Routes

To handle any unmatched routes, define a catch-all route using the * symbol:

'*': NotFound,

You can optionally name the parameter, which allows you to access the unmatched part of the URL via route.params similar to dynamic routes:

'*notfound': NotFound,

Layouts

Define a wrapping component for routes at the same level or below using layouts:

'/about': {
	'/': About,
	'/work': Work,
	'/team': Team,
	layout: AboutLayout,
},

This layout component must render its children:

AboutLayout.svelte

<script lang="ts">
	import type { Snippet } from 'svelte';

	let { children }: { children: Snippet } = $props();
</script>

<div class="wrapper">
	{@render children()}
</div>

NOTE

When navigating between routes that share the same layout, the layout component persists without being recreated. This prevents unnecessary side effect triggers.

WARNING

Layouts can only be used in tree structure, which means that doing the following will not work:

'/about': About,
'/about/layout': AboutLayout, // ❌ Won't work

Break Out of Layouts

Sometimes you may want certain routes to ignore their parent's layout. You can exclude a route from inheriting its parent layout by wrapping the route segment in parentheses:

'/about': {
	'/': About, // Uses AboutLayout
	'/work': {
		"/": Work, // Uses AboutLayout
		"/(clients)": Clients, // Ignores AboutLayout
	},
	layout: AboutLayout,
},

This pattern works for all route types, including dynamic segments and catch-all routes:

// Dynamic route that ignores parent layout
"/(:id)": PostId,

// Catch-all route that ignores parent layout
"(*notfound)": NotFound,

This technique allows you to selectively bypass layouts while maintaining your overall route hierarchy.