# Core features

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Chat is is designed to support in-session text communication. Zoom truncates messages exceeding a binary size of 10,000 bytes. As a best practice, we recommend a limit of 1000 characters per message.

While in a session, users can send chat messages to each other. Two main components within the SDK help you implement in-session messaging:

-   An instance of `ZMVideoSDKChatHelper` provides methods to send and receive messages in a session.
-   The `onChatNewMessageNotify` callback from your `ZMVideoSDKDelegate` confirms the delivery of a message.

For sending files and tracking transfer status, see [Send files in chat](/docs/video-sdk/macos/chat/send-files-in-chat/). For per-message metadata, see [Chat message details](/docs/video-sdk/macos/chat/chat-message-details/).

## Send a private message

Users can send a message privately to a single user.

```swift
// Get the ZMVideoSDKChatHelper to perform chat actions.
if let chatHelper = ZMVideoSDK.shared()?.getChatHelper() {
    // Check if chat is enabled in this session.
    if chatHelper.isChatDisabled() == false, chatHelper.isPrivateChatDisabled() == false {
        // Send message to user.
        chatHelper.sendChat(to: user, content: message)
    }
}
```

```objectivec
// Get the ZMVideoSDKChatHelper to perform chat actions.
ZMVideoSDKChatHelper *chatHelper = [[ZMVideoSDK sharedVideoSDK] getChatHelper];
// Check if chat is enabled in this session.
if ([chatHelper IsChatDisabled] == NO && [chatHelper IsPrivateChatDisabled] == NO) {
    // Send message to user.
    [chatHelper SendChatToUser:user Content:message];
}
```

## Send a public message

Users can send a message publicly to all users in the session.

```swift
// Get the ZMVideoSDKChatHelper to perform chat actions.
if let chatHelper = ZMVideoSDK.shared()?.getChatHelper() {
    // Check if chat is enabled in this session.
    if chatHelper.isChatDisabled() == false {
        // Send message to all users in this session.
        chatHelper.sendChat(toAll: message)
    }
}
```

```objectivec
// Get the ZMVideoSDKChatHelper to perform chat actions.
ZMVideoSDKChatHelper *chatHelper = [[ZMVideoSDK sharedVideoSDK] getChatHelper];
// Check if chat is enabled in this session.
if ([chatHelper IsChatDisabled] == NO) {
    // Send message to all users in this session.
    [chatHelper SendChatToAll:message];
}
```

## Receive incoming messages

To be notified when a message is received, use `onChatNewMessageNotify` within `ZMVideoSDKDelegate`. The `chatMessage` parameter contains information about the message, including a `ZMVideoSDKUser` info object for both the sender and recipient (if applicable).

```swift
func onChatNewMessageNotify(_ helper: ZMVideoSDKChatHelper!, message chatMessage: ZMVideoSDKChatMessage!) {
    // Message contains the info about a chat message.
    if let content = chatMessage.content, let senderName = chatMessage.sendUser.getName() {
        print("\(senderName) sent a message: \(content)")
    }
}
```

```objectivec
- (void)onChatNewMessageNotify:(ZMVideoSDKChatHelper *)helper message:(ZMVideoSDKChatMessage *)chatMessage {
    // Message contains the info about a chat message.
    NSString *content = chatMessage.content;
    ZMVideoSDKUser *sender = chatMessage.sendUser;
    NSLog(@"%@ sent a message: %@", [sender getName], content);
}
```

For more information on how to use the `ZMVideoSDKUser` object, see [Sessions](/docs/video-sdk/macos/sessions/).