Screen Sharing on Website

Screen Sharing Implementation on Website

Screen demonstration in browser works via getDisplayMedia() API—user selects what to show: entire screen, window, or tab. Then the stream is sent via WebRTC as a separate video track.

Native Browser API

async function startScreenShare(): Promise<MediaStream> {
  const stream = await navigator.mediaDevices.getDisplayMedia({
    video: {
      displaySurface: 'monitor',  // 'monitor' | 'window' | 'browser'
      width: { ideal: 1920 },
      height: { ideal: 1080 },
      frameRate: { ideal: 30, max: 60 },
    },
    audio: {
      echoCancellation: false,
      noiseSuppression: false,
    },
    preferCurrentTab: false,
  });

  return stream;
}

Screen Share Component

import { useRef, useState, useCallback } from 'react';

function ScreenShareButton({ peerConnection }: { peerConnection: RTCPeerConnection | null }) {
  const [isSharing, setIsSharing] = useState(false);
  const screenStreamRef = useRef<MediaStream | null>(null);
  const screenSenderRef = useRef<RTCRtpSender | null>(null);

  const startSharing = useCallback(async () => {
    try {
      const stream = await startScreenShare();
      screenStreamRef.current = stream;

      const [videoTrack] = stream.getVideoTracks();
      const [audioTrack] = stream.getAudioTracks();

      if (peerConnection) {
        const senders = peerConnection.getSenders();
        const videoSender = senders.find(s => s.track?.kind === 'video');

        if (videoSender) {
          await videoSender.replaceTrack(videoTrack);
          screenSenderRef.current = videoSender;
        } else {
          screenSenderRef.current = peerConnection.addTrack(videoTrack, stream);
        }

        if (audioTrack) {
          peerConnection.addTrack(audioTrack, stream);
        }
      }

      setIsSharing(true);
      videoTrack.addEventListener('ended', stopSharing);
    } catch (err) {
      if ((err as DOMException).name !== 'NotAllowedError') {
        console.error('Screen share error:', err);
      }
    }
  }, [peerConnection]);

  const stopSharing = useCallback(async () => {
    screenStreamRef.current?.getTracks().forEach(t => t.stop());

    if (screenSenderRef.current && peerConnection) {
      const cameraStream = await navigator.mediaDevices.getUserMedia({ video: true });
      const [cameraTrack] = cameraStream.getVideoTracks();
      await screenSenderRef.current.replaceTrack(cameraTrack);
    }

    setIsSharing(false);
  }, [peerConnection]);

  return (
    <button
      onClick={isSharing ? stopSharing : startSharing}
      className={`p-3 rounded-full ${isSharing ? 'bg-red-600 text-white' : 'bg-gray-700 text-white'}`}
    >
      {isSharing ? 'Stop' : 'Share Screen'}
    </button>
  );
}

LiveKit Integration

import { createLocalScreenTracks, Track } from 'livekit-client';

async function shareScreen(room: Room) {
  const screenTracks = await createLocalScreenTracks({
    audio: true,
    video: {
      width: 1920,
      height: 1080,
      frameRate: 30,
    },
  });

  await room.localParticipant.publishTrack(screenTracks[0], {
    name: 'screen',
    source: Track.Source.ScreenShare,
  });

  if (screenTracks[1]) {
    await room.localParticipant.publishTrack(screenTracks[1], {
      name: 'screen-audio',
      source: Track.Source.ScreenShareAudio,
    });
  }

  screenTracks[0].on('ended', async () => {
    await room.localParticipant.unpublishTrack(screenTracks[0]);
  });
}

Displaying Another's Screen

function RemoteScreenShare({ participant }: { participant: RemoteParticipant }) {
  const videoRef = useRef<HTMLVideoElement>(null);

  const screenTrack = [...participant.videoTracks.values()]
    .find(pub => pub.source === Track.Source.ScreenShare)?.track;

  useEffect(() => {
    if (!screenTrack || !videoRef.current) return;
    screenTrack.attach(videoRef.current);
    return () => { screenTrack.detach(videoRef.current!); };
  }, [screenTrack]);

  if (!screenTrack) return null;

  return (
    <div className="fixed inset-0 z-50 bg-black flex items-center justify-center">
      <video ref={videoRef} autoPlay playsInline
        className="max-w-full max-h-full" />
      <span className="absolute top-4 left-4 text-white bg-black/60 px-3 py-1 rounded">
        {participant.name} is sharing screen
      </span>
    </div>
  );
}

Timeline

Screen sharing via getDisplayMedia in P2P—1 day. LiveKit/Daily integration in group—1–2 days.