# MQTT Retained Message
EMQX implements the retained message feature of MQTT. You can flag one message published under a certain topic as `Retained` and save it as a persistent message on the EMQX. When any new subscribers subscribe to a topic that matches the topic of the retained message, they immediately receive that message, even if it was published before they subscribed to the topic.
You can use client tools to connect to EMQX and try this messaging service. This section introduces how to use the [MQTTX Desktop](https://mqttx.app/) and [MQTTX CLI](https://mqttx.app/cli) to simulate clients and see how a retained message is published and received.
:::tip Prerequisites
- Knowledge about MQTT [Retained Message](./mqtt-concepts.md)
- Basic publishing and subscribing operations using [MQTTX](./publish-and-subscribe.md)
:::
## Publish Retained Message with 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. After the successful connection, type the topic heading `sensor/t1` in the text box and compose the message payload as shown in the screenshot. Click the send button. A message to the topic `sensor/t1` appears in the message dialogue.
4. Publish two retained messages with the topic `sensor/t2`.
- Enter `1` as the first message. Select **Retain**. Click the send button.
- Enter `2` as the second message. Click the send button.
5. Click the **+** -> **New Connection** in the **Connections** pane to create a subscription `Subscriber` as a client that receives messages.
5. Click **+ New Subscription** to subscribe to the topic `sensor/+`. Click the **Confirm** button.
:::tip
With the topic set to `sensor/+`, both `sensor/t1` and `sensor/t2` are subscribed. For more information on topics and wildcards, see [Understanding MQTT Topics & Wildcards by Case](https://www.emqx.com/en/blog/advanced-features-of-mqtt-topics).
:::
You will see that the client `Subscriber` only receives the last retained message but not the first message with the topic `sensor/t1` and the first retained message with the topic `sensor/t2`, because EMQX only stores the latest retained message of each topic.
Now you have tried using the MQTTX Client to send a retained message. You can also check the latest retained message stored in the EMQX through the Dashboard, see [View Retained Message in Dashboard](#view-retained-message-in-dashboard).
## Publish Retained Message with MQTTX CLI
1. Initiate a connection request with one client.
1. Use the following command to publish a retained message. Set the topic to `t/1`, payload to `A retained message from MQTTX CLI`, and `retain = true`：
```bash
mqttx pub -t 't/1' -m 'A retained message from MQTTX CLI' --retain true -h 'localhost' -p 1883
```
3. Initiate another new client connection request to the same broker. Subscribe to the topic `t/1` with the new client. It will receive the retained message.
If you continuously create new clients and let them subscribe to the topic `t/1`, all new clients you created will receive the retained message.
```bash
$ mqttx sub -t 't/1' -h 'localhost' -p 1883 -v
topic: t/1
payload: A retained message from MQTTX CLI
retain: true
```
3. Publish an empty message to clear the retained message:
```bash
mqttx pub -t 't/1' -m '' --retain true -h 'localhost' -p 1883
```
4. Initiate a new client connection and subscribe to the topic `t/1`. No retained messages are received, indicating the retained message is cleared.
## View Retained Message in Dashboard
When you publish a retained message, EMQX will save this message in the system. you can view this message on the Retained Messages list page. When you subscribe to the topic of this retained message, EMQX will publish this message to the topic, and you can receive this message immediately by subscribing to the topic.
The default expiration time of the retained message is never expired unless you manually delete this message.
### Retained Messages List
In the **Monitoring** -> **Retained Messages** page, you can view all the retained messages in the system, including the topic, QoS, publish time, and client ID. The search box allows for filtering through search, and it supports topic wildcards.
The page also provides options to view the payload of a retained message and delete it using the **Show Payload** and **Delete** buttons respectively. You can refresh the list using the **Refresh** button and access the retained message settings page using the **Settings** button.
You can see the following 3 types of retained messages from [system topics](./mqtt-concepts.md) by default:
- $SYS/brokers/+/sysdescr: System description of the current EMQX node
- $SYS/brokers/+/version: Version number of the current EMQX node
- $SYS/brokers - Number and name of all nodes of the current EMQX
### Delete Retained Message
To delete a retained message in EMQX, you can either publish an empty message to the topic of the retained message in the client or use the EMQX Dashboard. In the Dashboard, you can click the **Delete** button for a specific retained message to remove it. You can also delete all retained messages on the cluster by using the **Clear All** button. Additionally, you can also set the expiration time for retained messages on the Retained Messages configuration page, allowing EMQX to automatically delete them when they expire.