<p>Initiates sign-in for a user in the Amazon Cognito user directory. You can't sign in a user with a federated IdP with <code>InitiateAuth</code>. For more information, see <a href="https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-pools-identity-federation.html"> Adding user pool sign-in through a third party</a>.</p> <note> <p>This action might generate an SMS text message. Starting June 1, 2021, US telecom carriers require you to register an origination phone number before you can send SMS messages to US phone numbers. If you use SMS text messages in Amazon Cognito, you must register a phone number with <a href="https://console.aws.amazon.com/pinpoint/home/">Amazon Pinpoint</a>. Amazon Cognito uses the registered number automatically. Otherwise, Amazon Cognito users who must receive SMS messages might not be able to sign up, activate their accounts, or sign in.</p> <p>If you have never used SMS text messages with Amazon Cognito or any other Amazon Web Service, Amazon Simple Notification Service might place your account in the SMS sandbox. In <i> <a href="https://docs.aws.amazon.com/sns/latest/dg/sns-sms-sandbox.html">sandbox mode</a> </i>, you can send messages only to verified phone numbers. After you test your app while in the sandbox environment, you can move out of the sandbox and into production. For more information, see <a href="https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-identity-pools-sms-userpool-settings.html"> SMS message settings for Amazon Cognito user pools</a> in the <i>Amazon Cognito Developer Guide</i>.</p> </note>

{
  "success": true,
  "data": {
    "id": "abc123",
    "created_at": "2025-01-01T00:00:00Z"
  }
}

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid request parameters"
  }
}