# Auto Subscribe
Auto Subscribe is an extended MQTT feature supported by EMQX. With **Auto Subscription** enabled, users can set multiple EMQX rules. After a client is successfully connected to EMQX, EMQX will complete the subscription process for the client automatically, and the clients no longer need to send `SUBSCRIBE` requests.
Before EMQX 5.0, this feature is called **Proxy Subscription**.
## Configure Auto Subscribe via Dashboard
1. Open EMQX Dashboard. In the left navigation menu, click **Management** -> **Auto Subscribe**.
2. On the **Auto Subscribe** page, click the **+ Add** button at the upper right corner.
3. In the pop-up dialog box, type the test topic `a/1` in the **Topic** text box. Leave other settings as default.
- **Topic**: Type the topic that is automatically subscribed to for the client. You can dynamically build the topic using placeholders. For details, see [Placeholders](#placeholders).
- **QoS**: Specify the quality of service of the topic. Options: `0`, `1`, and `2`.
- **No local**: Options: `False` or `True`.
- **Retain as Published**: Specify if the message sent with the specified topic will be retained. Options: `False` or `True`.
- **Retained Handling**: Options: `0`, `1`, and `2`.
Click the **Add** button on the dialogue box. The auto subscribe topic `a/1` is created successfully.
Now the auto subscription function is enabled. New subscribers will subscribe to the topic `a/1` automatically once they are connected to the broker.
## Try Auto Subscription Using MQTTX Desktop
The topic `a/1` is configured as the auto-subscribe topic in [Configure Auto Subscribe via Dashboard](#configure-auto-subscribe-via-dashboard). The following procedure demonstrates how a client subscribes to the topic `a/1` automatically once it is connected to the broker.
:::tip Prerequisite
Basic publishing and subscribing operations using [MQTTX Desktop](./publish-and-subscribe.md#mqttx-desktop).
:::
1. Start EMQX and MQTTX Desktop. Click the **New Connection** to create a client connection as a publisher.
- Enter `Demo` in the **Name** field.
- Enter the localhost `127.0.0.1` in **Host** to use as an example in this demonstration.
- Leave other settings as default and click **Connect**.
::: tip
More detailed instructions on creating an MQTT connection are introduced in [MQTTX Desktop](./publish-and-subscribe.md#mqttx-desktop).
:::
3. Create another MQTT client connection named `Subscriber`.
3. Select client `Demo` in the **Connections** pane. Enter `a/1` as the topic. Send a message to this topic.
- The client `Subscriber` receives the message automatically without creating a new subscription.
- The client `Demo` also receives the message as it is also a new connection.
::: tip
In the publish/subscribe pattern, a client can be both sender and subscriber.
:::
4. Go to EMQX Dashboard. Click **Monitoring** -> **Subscriptions** from the left navigation menu. It shows two subscriptions automatically subscribe to the topic `a/1`.
## Try Auto Subscription using MQTTX CLI
:::tip Prerequisite
Basic publishing and subscribing operations using [MQTTX CLI](./publish-and-subscribe.md#mqttx-cli)
:::
1. Create a new connection with client ID as `emqx_c`.
```bash
mqttx conn -i emqx_c
```
2. Go to EMQX Dashboard. Click **Monitoring** ->**Subscriptions** in the left navigation menu. It shows the client `emqx_c` subscribes to the topic `a/1`.
## Placeholders
Auto Subscribe supports placeholders to dynamically build topics. The format of the placeholder is `${}`. The variables supported by the placeholder are:
- `${clientid}`: Client ID.
- `${username}`: Client username.
- `${host}`: IP address when the client connects to EMQX.
For example, when the client ID is `emqx_c` and the configured topic is `a/${clientid}`, the client will automatically subscribe to the topic `a/emqx_c` after connecting to EMQX.