Nuxt CLI has built-in [dotenv](https://github.com/motdotla/dotenv) support in development mode and when running [`nuxi build`](/docs/api/commands/build) and [`nuxi generate`](/docs/api/commands/generate).
In addition to any process environment variables, if you have a `.env` file in your project root directory, it will be automatically loaded **at dev, build and generate time**. Any environment variables set there will be accessible within your `nuxt.config` file and modules.
If you want to use a different file - for example, to use `.env.local` or `.env.production` - you can do so by passing the `--dotenv` flag when using `nuxi`.
```bash [Terminal]
npx nuxi dev --dotenv .env.local
```
When updating `.env` in development mode, the Nuxt instance is automatically restarted to apply new values to the `process.env`.
Your `.env` file will not be read at this point. How you do this is different for every environment.
For local production preview purpose, we recommend using [`nuxi preview`](/docs/api/commands/preview) since using this command, the `.env` file will be loaded into `process.env` for convenience. Note that this command requires dependencies to be installed in the package directory.
If you want to use environment variables set at build time but do not care about updating these down the line (or only need to update them reactively _within_ your app) then `appConfig` may be a better choice. You can define `appConfig` both within your `nuxt.config` (using environment variables) and also within an `~/app.config.ts` file in your project.
