# streamId property Null safety

String streamId
read / write

Field description: bound Tencent Cloud CSS CDN stream ID, which is optional. After setting this field, you can play back the user's audio/video stream on Tencent Cloud Live CDN through a standard live streaming scheme (FLV or HLS).

Recommended value: this parameter can contain up to 64 bytes and can be left empty. We recommend you use `sdkappid_roomid_userid_main` as the `streamid`, which is easier to identify and will not cause conflicts in your multiple applications.

Note: to use Tencent Cloud CSS CDN, you need to enable the relayed live streaming feature on the "Function Configuration" page in the console first.

For more information, please see CDN Relayed Live Streaming.

## Implementation

    String streamId;