svelte/documentation/docs/02-template-syntax/04-special-tags.md

---
title: Special tags
---

## {@html ...}

```svelte
<!--- copy: false --->
{@html expression}
```

In a text expression, characters like `<` and `>` are escaped; however, with HTML expressions, they're not.

The expression should be valid standalone HTML — `{@html "<div>"}content{@html "</div>"}` will _not_ work, because `</div>` is not valid HTML. It also will _not_ compile Svelte code.

> Svelte does not sanitize expressions before injecting HTML. If the data comes from an untrusted source, you must sanitize it, or you are exposing your users to an XSS vulnerability.

```svelte
<div class="blog-post">
	<h1>{post.title}</h1>
	{@html post.content}
</div>
```

## {@debug ...}

```svelte
<!--- copy: false --->
{@debug}
```

```svelte
<!--- copy: false --->
{@debug var1, var2, ..., varN}
```

The `{@debug ...}` tag offers an alternative to `console.log(...)`. It logs the values of specific variables whenever they change, and pauses code execution if you have devtools open.

```svelte
<script>
	let user = {
		firstname: 'Ada',
		lastname: 'Lovelace'
	};
</script>

{@debug user}

<h1>Hello {user.firstname}!</h1>
```

`{@debug ...}` accepts a comma-separated list of variable names (not arbitrary expressions).

```svelte
<!-- Compiles -->
{@debug user}
{@debug user1, user2, user3}

<!-- WON'T compile -->
{@debug user.firstname}
{@debug myArray[0]}
{@debug !isReady}
{@debug typeof user === 'object'}
```

The `{@debug}` tag without any arguments will insert a `debugger` statement that gets triggered when _any_ state changes, as opposed to the specified variables.

## {@const ...}

```svelte
<!--- copy: false --->
{@const assignment}
```

The `{@const ...}` tag defines a local constant.

```svelte
<script>
	export let boxes;
</script>

{#each boxes as box}
	{@const area = box.width * box.height}
	{box.width} * {box.height} = {area}
{/each}
```

`{@const}` is only allowed as direct child of `{#if}`, `{:else if}`, `{:else}`, `{#each}`, `{:then}`, `{:catch}`, `<Component />` or `<svelte:fragment />`.