# no-duplicated-enum-values

Requires all values in an `enum` to be unique.

| OAS | Compatibility |
|  --- | --- |
| 2.0 | ✅ |
| 3.0 | ✅ |
| 3.1 | ✅ |
| 3.2 | ✅ |


| AsyncAPI | Compatibility |
|  --- | --- |
| 2.6 | ✅ |
| 3.0 | ✅ |


| Arazzo | Compatibility |
|  --- | --- |
| 1.0 | ✅ |


## API design principles

A duplicated value in an `enum` is always a mistake:
it adds noise for readers, and some tools reject such schemas because JSON Schema requires `enum` values to be unique.
This rule catches copy-paste errors early in your API definition.

## Configuration

| Option | Type | Description |
|  --- | --- | --- |
| severity | string | Possible values: `off`, `warn`, `error`. Default is `warn` in the recommended configuration. |


Example configuration:

```yaml
rules:
  no-duplicated-enum-values: error
```

## Examples

Example of **incorrect** enum values (duplicated value `red`):

```yaml
schemas:
  Color:
    type: string
    enum:
      - red
      - green
      - red
```

Example of **correct** enum values (all values are unique):

```yaml
schemas:
  Color:
    type: string
    enum:
      - red
      - green
```

## Related rules

- [no-enum-type-mismatch](/docs/cli/rules/common/no-enum-type-mismatch)


## Resources

- [Rule source](https://github.com/Redocly/redocly-cli/blob/main/packages/core/src/rules/common/no-duplicated-enum-values.ts)

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