---
title: "Custom message"
section: "build-a-backend/functions/examples"
platforms: ["android", "angular", "flutter", "javascript", "nextjs", "react", "react-native", "swift", "vue"]
gen: 2
last-updated: "2025-04-09T18:10:02.000Z"
url: "https://docs.amplify.aws/react/build-a-backend/functions/examples/custom-message/"
---

You can use `defineAuth` and `defineFunction` to create an [Amazon Cognito custom message AWS Lambda trigger](https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-custom-message.html) thats sends an custom email or phone verification message, or a multi-factor authentication (MFA) code.

To get started, install `@types/aws-lambda` package that will be used to define the type of the handler:

```bash title="Terminal" showLineNumbers={false}
npm add --save-dev @types/aws-lambda
```

Next, create a new directory and a resource file, `amplify/auth/custom-message/resource.ts`. Then, define the function with `defineFunction`:

```ts title="amplify/auth/custom-message/resource.ts"
import { defineFunction } from '@aws-amplify/backend';

export const customMessage = defineFunction({
  name: "custom-message",
  resourceGroupName: 'auth'
});
```

Next, create the corresponding handler file, `amplify/auth/custom-message/handler.ts`, file with the following contents:

<Callout>
The input event for the `CustomMessage_AdminCreateUser` trigger source includes both a username and verification code. Admin-created users must receive both their username and code in order to sign in and thus you must include both the `usernameParameter` and `codeParameter` in your message template.
</Callout>

```ts title="amplify/auth/custom-message/handler.ts" 
import type { CustomMessageTriggerHandler } from "aws-lambda";

export const handler: CustomMessageTriggerHandler = async (event) => {
  if (event.triggerSource === "CustomMessage_ForgotPassword") {
    const locale = event.request.userAttributes["locale"];
    if (locale === "en") {
      event.response.emailMessage = `Your new one-time code is ${event.request.codeParameter}`;
      event.response.emailSubject = "Reset my password";
    } else if (locale === "es") {
      event.response.emailMessage = `Tu nuevo código de un solo uso es ${event.request.codeParameter}`;
      event.response.emailSubject = "Restablecer mi contraseña";
    }
  }

  if (event.triggerSource === "CustomMessage_AdminCreateUser") {
    event.response.emailMessage = `Your username is ${event.request.usernameParameter} and your temporary password is ${event.request.codeParameter}`;
    event.response.emailSubject = 'Welcome to Example App';
  }

  return event;
};
```
 

Lastly, set the newly created function resource on your auth resource:

```ts title="amplify/auth/resource.ts"
import { defineAuth } from '@aws-amplify/backend';
import { customMessage } from "./custom-message/resource";

export const auth = defineAuth({
  // ...
  triggers: {
    customMessage,
  }
});
```

After deploying the changes, whenever a user with user attribute `locale` set to `es` attempts to reset a password they will receive an email with a one-time code in Spanish.