Post confirmation Lambda trigger - Amazon Cognito

Post confirmation Lambda trigger

Amazon Cognito invokes this trigger after a signed-up user confirms their user account. In your post confirmation Lambda function, you can send custom messages or add custom API requests. For example, you can query an external system and populate additional attributes to the user. Amazon Cognito invokes this trigger only for user who sign up in your user pool, not for user accounts that you create with your administrator credentials.

The request contains the current attributes for the confirmed user.

Post confirmation Lambda flows

Client confirm sign-up flow

Client confirm sign-up flow

Server confirm sign-up flow

Server confirm sign-up

Confirm forgot password flow

Confirm forgot password flow

Post confirmation Lambda trigger parameters

The request that Amazon Cognito passes to this Lambda function is a combination of the parameters below and the common parameters that Amazon Cognito adds to all requests.

{ "request": { "userAttributes": { "string": "string", . . . }, "clientMetadata": { "string": "string", . . . } }, "response": {} }

Post confirmation request parameters


One or more key-value pairs representing user attributes.


One or more key-value pairs that you can provide as custom input to the Lambda function that you specify for the post confirmation trigger. You can pass this data to your Lambda function by using the ClientMetadata parameter in the following API actions: AdminConfirmSignUp, ConfirmForgotPassword, ConfirmSignUp, and SignUp.

Post confirmation response parameters

No additional return information is expected in the response.

User confirmation tutorials

The post confirmation Lambda function is triggered just after Amazon Cognito confirms a new user. See these user confirmation tutorials for JavaScript, Android, and iOS.

Platform Tutorial
JavaScript Identity SDK Confirm users with JavaScript
Android Identity SDK Confirm users with Android
iOS Identity SDK Confirm users with iOS

Post confirmation example

This example Lambda function sends a confirmation email message to your user using Amazon SES. For more information see Amazon Simple Email Service Developer Guide.

// Import required AWS SDK clients and commands for Node.js. Note that this requires // the `@aws-sdk/client-ses` module to be either bundled with this code or included // as a Lambda layer. import { SES, SendEmailCommand } from "@aws-sdk/client-ses"; const ses = new SES(); const handler = async (event) => { if ( { await sendTheEmail(, `Congratulations ${event.userName}, you have been confirmed.` ); } return event; }; const sendTheEmail = async (to, body) => { const eParams = { Destination: { ToAddresses: [to], }, Message: { Body: { Text: { Data: body, }, }, Subject: { Data: "Cognito Identity Provider registration completed", }, }, // Replace source_email with your SES validated email address Source: "<source_email>", }; try { await ses.send(new SendEmailCommand(eParams)); } catch (err) { console.log(err); } }; export { handler };

Amazon Cognito passes event information to your Lambda function. The function then returns the same event object to Amazon Cognito, with any changes in the response. In the Lambda console, you can set up a test event with data that is relevant to your Lambda trigger. The following is a test event for this code sample:

{ "request": { "userAttributes": { "email": "", "email_verified": true } }, "response": {} }