No Virtual DOM.
Pure Surgical Reactivity.

Step inside the Svelte compiler engine. Witness how $state, $derived, and $effect turn into high-performance, pinpoint vanilla JavaScript without reconciliation diffing overhead.

Explore Concept Map Runes Sandbox AST Compiler

SignalTelemetry.svelte

let count = $state(3);

let multiplier = $state(2);

let total = $derived(count * multiplier);

$effect(() => console.log('Signal update:', count));

</script>

Signal: count

Signal: multiplier

$derived(count × multiplier):6

Architectural Comparison

Virtual DOM vs Svelte Compiler

Why shifting work from browser runtime to compile-time creates faster web applications.

Runtime VDOM ModelReact / Vue 2

Every state change generates a brand new Virtual DOM JavaScript tree. The runtime recursively diffs the new tree against the old tree to find mutations before patching the real DOM.

1. State mutation: count = 4

2. Render function re-executes whole component

3. Build in-memory VNode tree (allocates objects)

4. Diff VNode tree vs Previous VNode tree

5. Patch browser DOM

Svelte 5 Signals EngineZero VDOM

The Svelte compiler transforms templates into pinpoint DOM updates at build time. When state changes, only the exact text node pointer is updated directly.

1. State mutation: count.set(4)

2. Signal notifies exact consumer effect

3. Direct mutate: count_text_node.data = 4

✓ 0 reconciliation passes · 0 tree diffing

Curriculum Roadmap