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Amazon Cognito
Developer Guide

Custom Message Lambda Parameters

Amazon Cognito invokes this trigger before sending an email or phone verification message or a multi-factor authentication (MFA) code, allowing you to customize the message dynamically. Static custom messages can be edited in the Message Customizations tab of the Amazon Cognito console.

The request includes codeParameter, which is a string that acts as a placeholder for the code that's being delivered to the user. Insert the codeParameter string into the message body, at the position where you want the verification code to be inserted. On receiving this response, the Amazon Cognito service replaces the codeParameter string with the actual verification code.

Note

A custom message Lambda function with the CustomMessage_AdminCreateUser trigger returns a user name and verification code and so the request must include both request.usernameParameter and request.codeParameter.

"request": { "userAttributes": { "string": "string", .... }, "codeParameter": "string", "usernameParameter": "string" // The username parameter is required for the admin create user flow. }
userAttributes

One or more name-value pairs representing user attributes.

codeParameter

A string for you to use as the placeholder for the verification code in the custom message.

username

The username parameter. It is a required request parameter for the admin create user flow.

In the response, you specify the custom text to use in messages to your users.

"response": { "smsMessage": "string", "emailMessage": "string", "emailSubject": "string"; }
smsMessage

The custom SMS message to be sent to your users. Must include the codeParameter value received in the request.

emailMessage

The custom email message to be sent to your users. Must include the codeParameter value received in the request.

emailSubject

The subject line for the custom message.