# Creating an AppInstance for Amazon Chime SDK messaging
Creating an AppInstance

To use Amazon Chime SDK messaging, you must first create an Amazon Chime SDK `AppInstance` in your AWS account.

**Topics**
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## Building an AppInstance
](#app-instance-steps)
+ [

## Creating an AppInstanceUser
](#create-app-instance-user)

## Building an AppInstance


**To create an `AppInstance` for messaging**

1. In the CLI, run `aws chime-sdk-identity create-app-instance --name NameOfAppInstance.`

1. In the create response, make note of the `AppInstanceArn`. `arn:aws:chime:region: aws_account_id:app-instance/app_instance_id`.

## Creating an AppInstanceUser


Once you create an `AppInstance`, you create an `AppInstanceUser` in that `AppInstance`. You typically do this when a user first registers or logs in to your app. You can also create an `AppInstanceUser` that acts on behalf of your back-end services.

The following example shows how to create a back-end `AppInstanceUser`:

```
aws chime-sdk-identity create-app-instance-user \
    --app-instance-arn "app_instance_arn" \
    --app-instance-user-id "back-end-worker" \
    --name "back-end-worker"
```

In the create response, note the `AppInstanceUserArn`. It takes this form: `arn:aws:chime:region: aws_account_id:app-instance/app_instance_id/user/app_instance_user_id`. In this example, `app_instance_user_id` is "back-end-worker."

**Note**  
As a best practice, when creating an `AppInstanceUser` for a client application, have the `AppInstanceUserId` match an existing unique ID for that user, such as the `sub` of an identity provider. The name is an optional placeholder that is attached to some API entities, such as a message sender. It allows you to control the display name of a user in one place, rather then needing to look it up from `AppInstanceUser` ARN, which is also attached as the sender of a message.