svelte/site/content/faq/500-what-about-typescript-support.md

---
question: What about TypeScript support?
---

You need to install a preprocessor such as [svelte-preprocess](https://github.com/sveltejs/svelte-preprocess). You can run type checking from the command line with [svelte-check](https://www.npmjs.com/package/svelte-check).

To declare the type of a reactive variable in a Svelte template, you should use the following syntax:

```
let x: number;
$: x = count + 1;
```

To import a type or interface make sure to use [TypeScript's `type` modifier](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-8.html#type-only-imports-and-export):

```
import type { SomeInterface } from './SomeFile';
```

You must use the `type` modifier because `svelte-preprocess` doesn't know whether an import is a type or a value — it only transpiles one file at a time without knowledge of the other files and therefore can't safely erase imports which only contain types without this modifier present.