> ## Documentation Index
> Fetch the complete documentation index at: https://auth0-actions-triggers-prototype.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# IdentifierType

A string union type representing the valid methods for identifying a user during authentication. Used to constrain identifier inputs to one of three specific values.

```typescript theme={null}
type IdentifierType = "phone" | "email" | "username";
```

## Values

<ParamField body="&#x22;phone&#x22;" type="IdentifierType">
  A phone number identifier.
</ParamField>

<ParamField body="&#x22;email&#x22;" type="IdentifierType">
  An email address identifier.
</ParamField>

<ParamField body="&#x22;username&#x22;" type="IdentifierType">
  A username identifier.
</ParamField>