[Home](./index.md) > [@firebase/auth-types](./auth-types.md) > [AdditionalUserInfo](./auth-types.additionaluserinfo.md) > [providerId](./auth-types.additionaluserinfo.providerid.md) ## AdditionalUserInfo.providerId property Identifier for the provider used to authenticate this user. Signature: ```typescript readonly providerId: string | null; ```