# `env`

The `env` option allows you to customize the `redocly.yaml` configuration based on the current environment.
You can override the configuration by adding the necessary nested options directly or by creating an environment
configuration file in the **root** directory and referencing it in the `env` option.

## Options

| Option | Type | Description |
|  --- | --- | --- |
| preview | [[Redocly config](/docs/realm/config) or [Reference object](#reference-object)] | Configuration for the preview environment. |
| development | [[Redocly config](/docs/realm/config) or [Reference object](#reference-object)] | Configuration for the development environment. |
| production | [[Redocly config](/docs/realm/config) or [Reference object](#reference-object)] | Configuration for the production environment. |


### Reference object

| Option | Type | Description |
|  --- | --- | --- |
| $ref | string | Environment configuration file name |


## Examples

The following example demonstrates how to override specific configuration options inline within the `env` option:


```yaml
env:
  preview:
    breadcrumbs:
      hide: true
    logo:
      image: ./images/custom-logo.png
```

Or how to set the environment configuration for the `preview` environment by referencing an external file:


```yaml
env:
  preview:
    $ref: redocly.preview.yaml
```

The following example shows a `preview` environment configuration file that overrides the default configuration:

`redocly.preview.yaml`


```yaml
breadcrumbs:
  hide: true
logo:
  image: ./images/redocly.png
navbar:
  items:
    - label: External docs
      href: https://redocly.com
```

## Resources

- **[Configuration options](/docs/realm/config)** - Explore other project configuration options for comprehensive documentation and platform customization