pages/guides/typescript.mdx

---
title: Use TypeScript
description: An in-depth guide on configuring an Expo project with TypeScript.
---

import { Terminal } from '~/ui/components/Snippet';
import { BoxLink } from '~/ui/components/BoxLink';
import { GithubIcon } from '@expo/styleguide-icons';
import { Tabs, Tab, TabsGroup } from '~/ui/components/Tabs';

Expo has first-class support for [TypeScript](https://www.typescriptlang.org/). The JavaScript interface of the Expo SDK is completely written in TypeScript.

<BoxLink
  title="with-typescript"
  description="See the example project on GitHub."
  href="https://github.com/expo/examples/tree/master/with-typescript"
  Icon={GithubIcon}
/>

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## Get started

### Quick start with a template

The easiest way to get started is to initialize your new project using a TypeScript template:

<Terminal cmd={['$ npx create-expo-app -t expo-template-blank-typescript']} />

For npm, add the following `script` to the **package.json**:

{/* prettier-ignore */}
```json package.json
{
  "scripts": {
    "tsc": "tsc"
    /* @hide ... */ /* @end */
  }
}
```

Then, to type-check the project, run the following command:

<Tabs>
<Tab label="npm">

<Terminal cmd={['$ npm run tsc']} />

</Tab>

<Tab label="yarn">

<Terminal cmd={['$ yarn tsc']} />

</Tab>
</Tabs>

When you create new source files in your project you should use the **.ts** extension or the **.tsx** if the file includes React components.

### In an existing project

Rename files to convert them to TypeScript. For example, rename **App.js** to **App.tsx**. Use the **.tsx** extension if the file includes React components (JSX). If the file does not include any JSX, you can use the **.ts** file extension.

<Terminal cmd={['$ mv App.js App.tsx']} />

> **For SDK 48 and higher**, running `npx expo start` prompts you to install the required dependencies, such as `typescript` and `@types/react`. **For SDK 47 and below**, the command also prompts you to install `@types/react-native` as an additional dependency.

For npm, add the following `script` to the **package.json**:

{/* prettier-ignore */}
```json package.json
{
  "scripts": {
    "tsc": "tsc"
    /* @hide ... */ /* @end */
  }
}
```

You can now run `npm run tsc` or `yarn tsc` to type-check the project.

## Base configuration

> You can disable the TypeScript setup in Expo CLI with the environment variable `EXPO_NO_TYPESCRIPT_SETUP=1`

A project's **tsconfig.json** should extend the `expo/tsconfig.base` by default. This sets the following default [compiler options](https://www.typescriptlang.org/docs/handbook/compiler-options.html) (which can be overwritten in your project's **tsconfig.json**):

## Project configuration

Expo CLI will automatically modify your **tsconfig.json** to the preferred default which is optimized for universal React development:

```json tsconfig.json
{
  "extends": "expo/tsconfig.base",
  "compilerOptions": {}
}
```

The default configuration for TypeScript is user-friendly and encourages adoption. However, if you prefer strict type checking, you can enable it by adding `"strict": true` to the `compilerOptions`. We recommend enabling this to minimize the chance of introducing runtime errors.

Some language features may require additional configuration. For example, if want to use decorators you'll need to add the `experimentalDecorators` option. For more information on the available properties see the [TypeScript compiler options](https://www.typescriptlang.org/docs/handbook/compiler-options.html) documentation.

## Path aliases

> Available in SDK 49 and higher.

In SDK 49 projects, you'll need to enable path aliases in the project's [app config](/workflow/configuration/):

```json app.json
{
  "expo": {
    "experiments": {
      "tsconfigPaths": true
    }
  }
}
```

Expo CLI supports [path aliases](https://www.typescriptlang.org/docs/handbook/module-resolution.html#path-mapping) in your project's **tsconfig.json** automatically. This enables you to import modules using a custom alias instead of a relative path.

For example, if you have a file at **src/components/Button.tsx** and wish to import it using the alias **@/components/Button** as follows:

```tsx
import Button from '@/components/Button';
```

Then simply add the alias **@/\*** in the project's **tsconfig.json** and set it to the **src** directory:

```json tsconfig.json
{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "@/*": ["src/*"]
    }
  }
}
```

Consider the following when using path aliases:

- Restart Expo CLI after changing **tsconfig.json** to update path aliases. You don't need to clear the Metro cache when the aliases change.
- If not using TypeScript, **jsconfig.json** can serve as an alternative to **tsconfig.json**.
- Path aliases add additional resolution time when defined.
- Path aliases are only supported by Metro (including Metro web) and not by `@expo/webpack-config`.
- Bare projects require additional setup for this feature. See the [versioned Metro setup guide](/versions/latest/config/metro#bare-workflow-setup) for more information.

## Absolute imports

> Available in SDK 49 and higher.

In SDK 49 projects, you'll need to enable absolute imports in the project's [app config](/workflow/configuration/):

```json app.json
{
  "expo": {
    "experiments": {
      "tsconfigPaths": true
    }
  }
}
```

Absolute imports from the project root directory are enabled automatically when the project contains a **tsconfig.json** or **jsconfig.json** file. For example:

```tsx
import Button from 'src/components/Button';
// Imports `<project root>/src/components/Button`
```

You can modify the base directory in the tsconfig.json (or jsconfig.json) using the [baseUrl](https://www.typescriptlang.org/docs/handbook/module-resolution.html#base-url) option:

```json tsconfig.json
{
  "compilerOptions": {
    "baseUrl": "src"
  }
}
```

Consider the following when using absolute imports:

- [`compilerOptions.baseUrl`](https://www.typescriptlang.org/docs/handbook/module-resolution.html#base-url) is automatically set to `.` when the `tsconfig.json` or **jsconfig.json** file exists.
- Absolute imports in Node modules cannot be overwritten by absolute imports, as they take precedence.
- Restarting Expo CLI is necessary to update [`compilerOptions.baseUrl`](https://www.typescriptlang.org/docs/handbook/module-resolution.html#base-url) after modifying **the tsconfig.json**.
- If not using TypeScript, **jsconfig.json** can serve as an alternative to **tsconfig.json**.
- Absolute imports are only supported by Metro (including Metro web) and not by `@expo/webpack-config`.
- Bare projects require additional setup for this feature. See the [versioned Metro setup guide](/versions/latest/config/metro#bare-workflow-setup) for more information.

## TypeScript for config files

If you want to use TypeScript for configuration files such as **webpack.config.js**, **metro.config.js**, or **app.config.js**, additional setup is needed. You can utilize the [`ts-node` require hook](https://github.com/TypeStrong/ts-node#programmatic) to import TypeScript files within your JS config file, allowing TypeScript imports while keeping the root file as JavaScript.

<Tabs>
<Tab label="npm">

<Terminal cmd={['$ npm install ts-node typescript --save-dev']} />

</Tab>

<Tab label="yarn">

<Terminal cmd={['$ yarn add -D ts-node typescript']} />

</Tab>
</Tabs>

### webpack.config.js

> Install the `@expo/webpack-config` package.

```js webpack.config.js
require('ts-node/register');
module.exports = require('./webpack.config.ts');
```

```ts webpack.config.ts
import createExpoWebpackConfigAsync from '@expo/webpack-config/webpack';
import { Arguments, Environment } from '@expo/webpack-config/webpack/types';

module.exports = async function (env: Environment, argv: Arguments) {
  const config = await createExpoWebpackConfigAsync(env, argv);
  // Customize the config before returning it.
  return config;
};
```

### metro.config.js

```js metro.config.js
require('ts-node/register');
module.exports = require('./metro.config.ts');
```

```ts metro.config.ts
import { getDefaultConfig } from 'expo/metro-config';

const config = getDefaultConfig(__dirname);

module.exports = config;
```

### app.config.js

**app.config.ts** is supported by default. However, it doesn't support external TypeScript modules, or **tsconfig.json** customization. You can use the following approach to get a more comprehensive TypeScript setup:

```js app.config.js
require('ts-node/register');
module.exports = require('./app.config.ts');
```

```ts app.config.ts
import { ExpoConfig } from 'expo/config';

// In SDK 46 and lower, use the following import instead:
// import { ExpoConfig } from '@expo/config-types';

const config: ExpoConfig = {
  name: 'my-app',
  slug: 'my-app',
};

export default config;
```

## Learn how to use TypeScript

A good place to start learning TypeScript is the official [TypeScript Handbook](https://www.typescriptlang.org/docs/handbook/2/everyday-types.html).

**For TypeScript and React components,** we recommend referring to the [React TypeScript CheatSheet](https://github.com/typescript-cheatsheets/react) to learn how to type your React components in a variety of common situations.

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