# Core features

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Enhance the collaborative experience of a session by using the screen sharing feature provided by the Video SDK for macOS. This feature gives users the ability to share their screen's content on a macOS device.

## Screen sharing options

There are two different approaches for screen sharing with the Video SDK:

1. **Share the entire display**
2. **Share a specific window**

To use either method, retrieve a `ZMVideoSDKShareHelper` instance through the SDK.

```swift
let helper = ZMVideoSDK.shared()?.getShareHelper()
```

```objectivec
ZMVideoSDKShareHelper *helper = [[ZMVideoSDK sharedVideoSDK] getShareHelper];
```

After determining the type of share you are going to use, **obtain the ID** of the display or window you would like to share.

-   For **sharing a display**, use the [CGDirectDisplayID](https://developer.apple.com/documentation/coregraphics/cgdirectdisplayid).
-   For **sharing a window**, use the [CGWindowID](https://developer.apple.com/documentation/coregraphics/cgwindowid).

## Start sharing

After obtaining the ID of the window or display you intend to share with your session, pass it into the corresponding `startShare` method.

### Share a display

To share an entire display, pass its `CGDirectDisplayID` to `startShareScreen`.

```swift
helper?.startShareScreen(displayId, shareOption: ZMVideoSDKShareOption())
```

```objectivec
[helper startShareScreen:displayId shareOption:shareOptions];
```

### Share a window

To share a single window, pass its `CGWindowID` to `startShareView`.

```swift
helper?.startShareView(windowId, shareOption: ZMVideoSDKShareOption())
```

```objectivec
[helper startShareView:windowId shareOption:shareOptions];
```

## Verify screen share

After completing the above steps to share your screen, verify that your screen share has started by responding to the following callback to get notified when a user starts or stops screen sharing within your `ZMVideoSDKDelegate`.

```swift
func onUserShareStatusChanged(shareHelper: ZMVideoSDKShareHelper, user: ZMVideoSDKUser, shareAction: ZMVideoSDKShareAction) {
    switch shareAction.shareStatus {
    case .none:
        break
    // User has begun sharing.
    case .start:
        shareAction.getShareCanvas().subscribe(with: yourView, aspectMode: .original, resolution: .auto)
    case .pause:
        break
    case .resume:
        break
    // User has stopped sharing.
    case .stop:
        // Retrieve the share canvas and unsubscribe it from your view.
        shareAction.getShareCanvas().unSubscribe(with: yourView)
    default:
        break
    }
}
```

```objectivec
- (void)onUserShareStatusChanged:(ZMVideoSDKShareHelper*)shareHelper user:(ZMVideoSDKUser*)user shareAction:(ZMVideoSDKShareAction*)shareAction {
    switch (shareAction.shareStatus) {
        case ZMVideoSDKShareStatus_None:
            break;
        // User has begun sharing.
        case ZMVideoSDKShareStatus_Start:
            [[shareAction getShareCanvas] subscribeWithView:yourView aspectMode:ZMVideoSDKVideoAspect_Original resolution:ZMVideoSDKResolution_Auto];
        case ZMVideoSDKShareStatus_Pause:
            break;
        case ZMVideoSDKShareStatus_Resume:
            break;
        // User has stopped sharing.
        case ZMVideoSDKShareStatus_Stop:
            // Retrieve the share canvas and unsubscribe it from your view.
            [[shareAction getShareCanvas] unSubscribeWithView:yourView];
        default:
            break;
    }
}
```

To verify that the screen share data of a user is accessible on another device, subscribe to the user's share pipe.

```swift
let sharePipe = user.getSharePipe()
sharePipe?.subscribe(ZMVideoSDKResolution_720P, listener: self)
```

```objectivec
ZMVideoSDKRawDataPipe *sharePipe = [user getSharePipe];
[sharePipe subscribe:ZMVideoSDKResolution_720P listener:self];
```

## Share device audio

There are two aspects to this:

-   Starting a share with audio enabled.
-   Starting audio share.

### Start share with audio enabled

To include device audio when you begin sharing, create a `ZMVideoSDKShareOption` with `isWithDeviceAudio` enabled (and `isOptimizeForSharedVideo` for smoother video), then pass it to `startShareScreen` or `startShareView`.

```swift
let shareOptions = ZMVideoSDKShareOption()
shareOptions.isOptimizeForSharedVideo = true
shareOptions.isWithDeviceAudio = true
```

```objectivec
ZMVideoSDKShareOption *shareOption = [[ZMVideoSDKShareOption alloc] init];
shareOption.isOptimizeForSharedVideo = true;
shareOption.isWithDeviceAudio = true;
```

### Start sharing audio

To toggle device audio on a share that is already in progress, call `enableShareDeviceAudio` on the share helper.

```swift
helper?.enableShareDeviceAudio(true)
helper?.enableOptimize(forSharedVideo: true)
```

```objectivec
[helper enableShareDeviceAudio:true];
[helper enableOptimizeForSharedVideo:true];
```

To draw over shared content, see [Annotation](/docs/video-sdk/macos/share/annotation/). To subscribe to a specific share when a user has more than one, see [Handle multiple screen shares](/docs/video-sdk/macos/share/handle-multiple-shares/).