> For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt.

# mode

- **Type:** `'production' | 'development' | 'none'`

Sets the Rsbuild build mode. Each mode applies different defaults and optimizations; for example, `production` minifies code by default.

The Rsbuild `mode` value is also passed to Rspack's [mode](https://rspack.rs/config/mode) configuration.

:::tip
The `mode` value does not change which `.env` file loads because `.env` files resolve before the Rsbuild config file.

Use the `--env-mode` option in the Rsbuild CLI to specify the env mode. See ["Env mode"](/guide/advanced/env-vars.md#env-mode) for details.
:::

## Default values

The default value of `mode` depends on the `process.env.NODE_ENV` environment variable:

- If `NODE_ENV` is `production`, the default value is `production`.
- If `NODE_ENV` is `development`, the default value is `development`.
- If `NODE_ENV` has any other value, the default value is `none`.

If you set `mode`, the `NODE_ENV` value will be ignored.

```ts title="rsbuild.config.ts"
export default {
  mode: 'production',
};
```

### Command line

When using the Rsbuild CLI:

- `rsbuild` will set the default values of `NODE_ENV` and `mode` to `development`.
- `rsbuild build` and `rsbuild preview` will set the default values of `NODE_ENV` and `mode` to `production`.

### JavaScript API

When using the Rsbuild JavaScript API:

- [rsbuild.startDevServer](/api/javascript-api/instance.md#rsbuildstartdevserver) and [rsbuild.createDevServer](/api/javascript-api/instance.md#rsbuildcreatedevserver) will set the default values of `NODE_ENV` and `mode` to `development`.
- [rsbuild.build](/api/javascript-api/instance.md#rsbuildbuild) and [rsbuild.preview](/api/javascript-api/instance.md#rsbuildpreview) will set the default values of `NODE_ENV` and `mode` to `production`.

## Development mode

If `mode` is `development`:

- Enable HMR and register the [HotModuleReplacementPlugin](https://rspack.rs/plugins/hot-module-replacement-plugin).
- Generate JavaScript source maps, but do not generate CSS source maps. See [output.sourceMap](/config/output/source-map.md) for details.
- The `process.env.NODE_ENV` in the source code will be replaced with `'development'`.
- The `import.meta.env.MODE` in the source code will be replaced with `'development'`.
- The `import.meta.env.DEV` in the source code will be replaced with `true`.
- The `import.meta.env.PROD` in the source code will be replaced with `false`.
- Use [dev.assetPrefix](/config/dev/asset-prefix.md) as the URL prefix for static assets.

## Production mode

If `mode` is `production`:

- Enable JavaScript code minification and register the [SwcJsMinimizerRspackPlugin](https://rspack.rs/plugins/swc-js-minimizer-rspack-plugin).
- Enable CSS code minification and register the [LightningCssMinimizerRspackPlugin](https://rspack.rs/plugins/lightning-css-minimizer-rspack-plugin).
- JavaScript and CSS filenames include hash suffixes. See [output.filenameHash](/config/output/filename-hash.md).
- CSS Modules class names are shorter. See [cssModules.localIdentName](/config/output/css-modules.md#cssmoduleslocalidentname).
- JavaScript and CSS source maps are disabled. See [output.sourceMap](/config/output/source-map.md).
- The `process.env.NODE_ENV` in the source code will be replaced with `'production'`.
- The `import.meta.env.MODE` in the source code will be replaced with `'production'`.
- The `import.meta.env.DEV` in the source code will be replaced with `false`.
- The `import.meta.env.PROD` in the source code will be replaced with `true`.
- Use [output.assetPrefix](/config/output/asset-prefix.md) as the URL prefix for static assets.

## None mode

If `mode` is `none`:

- Do not enable any optimizations.
- The `process.env.NODE_ENV` in the source code will not be replaced.
- The `import.meta.env.MODE` in the source code will be replaced with `'none'`.
- The `import.meta.env.DEV` in the source code will be replaced with `false`.
- The `import.meta.env.PROD` in the source code will be replaced with `false`.
- Use [output.assetPrefix](/config/output/asset-prefix.md) as the URL prefix for static assets.