# Presence (/en/realtime-media/im/build/build-core-messaging/presence/web)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

The presence feature enables users to publicly display their online presence status and quickly determine the status of other users. Users can also customize their presence status, which adds fun and diversity to real-time chatting.

    The following illustration shows the implementation of creating a custom presence status and how various presence statues look in a contact list:

    ![1655302111155](https://web-cdn.agora.io/docs-files/1655302111155)

    This page shows how to use the Chat SDK to implement presence in your project.

    ## Understand the tech [#understand-the-tech-4]

    The Chat SDK allows you to implement the following features:

    The following figure shows the workflow of how clients subscribe to and publish presence statuses:

    Presence workflow

    ![1655308138447](https://web-cdn.agora.io/docs-files/1655308138447)

    ## Prerequisites [#prerequisites-4]

    Before proceeding, ensure that your environment meets the following requirements:

    * You have initialized the Chat SDK. For details, see [SDK quickstart](../../get-started-sdk).
    * You understand the API call frequency limit as described in [Limitations](../limitations).
    * You have activated the presence feature in [Agora Console](https://console.agora.io/v2).

    ## Implementation [#implementation-4]

    This section introduces how to implement presence functionalities in your project.

    ### Subscribe to the presence status of one or more users [#subscribe-to-the-presence-status-of-one-or-more-users-4]

    By default, you do not subscribe to any users. To subscribe to the presence statuses of the specified users, you can call `subscribePresence`. Whenever the specified users update their presence statuses, the `onPresenceStatusChange` callback is triggered, notifying you about the updated statuses asynchronously.

    The following code sample shows how to subscribe to the presence status of one or more users:

    ```javascript
    const options = {
      usernames: ["Alice", "Bob"],
      expiry: 7 * 24 * 3600,
    };
    chatClient.subscribePresence(options).then((res) => {
      console.log(res);
    });
    ```

    <CalloutContainer type="info">
      <CalloutDescription>
        You can subscribe to a maximum of 100 users at each call. The total subscriptions of each user cannot exceed 3,000. Once the number of subscriptions exceed the limit, the subsequent subscriptions with longer
        durations succeed and replace the existing subscriptions with shorter
        durations.

        The subscription duration can be a maximum of 30 days. When the
        subscription to a user expires, you need to subscribe to this user once
        again. If you subscribe to a user again before the current subscription
        expires, the duration is reset.
      </CalloutDescription>
    </CalloutContainer>

    ### Publish a custom presence status [#publish-a-custom-presence-status-4]

    You can call `publishPresence` to publish a custom status. Whenever your presence status updates, the users who subscribe to you receive the `onPresenceStatusChange` callback.

    The following code sample shows how to publish a custom status:

    ```javascript
    const options = {
      description: "custom presence",
    };
    chatClient.publishPresence(options).then((res) => {
      console.log(res);
    });
    ```

    ### Listen for presence status updates [#listen-for-presence-status-updates-4]

    Refer to the following code sample to listen for presence status updates:

    ```javascript
    // Adds the presence status listener.
    chatClient.addEventHandler('handlerId',{
      // Occurs when the presence statuses of the subscriptions update.
       onPresenceStatusChange: (msg) => {
           // You can implement subsequent settings in this callback.
            console.log('status updates'，msg)
       },
    })
    ```

    ### Unsubscribe from the presence status of one or more users [#unsubscribe-from-the-presence-status-of-one-or-more-users-4]

    You can call `unsubscribePresence` to unsubscribe from the presence statuses of the specified users, as shown in the following code sample:

    ```javascript
    const options = {
      usernames: ["Alice", "Bob"],
    };
    chatClient.unsubscribePresence(options).then((res) => {
      console.log(res);
    });
    ```

    ### Retrieve the list of subscriptions [#retrieve-the-list-of-subscriptions-4]

    You can call `getSubscribedPresencelist` to retrieve the list of your subscriptions in a paginated list, as shown in the following code sample:

    ```javascript
    const options = {
      pageNum: 0,
      pageSize: 50,
    };
    chatClient.getSubscribedPresenceList(options).then((res) => {
      console.log(res);
    });
    ```

    ### Retrieve the presence status of one or more users [#retrieve-the-presence-status-of-one-or-more-users-4]

    You can call `getPresenceStatus` to retrieve the current presence statuses of the specified users without the need to subscribe to them, as shown in the following code sample:

    ```javascript
    const options = {
      // usernames: The ID list of users whose presence status you retrieve.
      // You can pass in up to 100 user IDs.
      usernames: ["Alice", "Bob"],
    };
    chatClient.getPresenceStatus(options).then((res) => {
      console.log(res);
    });
    ```