Late 2016 MacBook Pro w/ TouchBar LG Ultrafine 5K display


Screen Sharing app connected to remote instance in the cloud


Very slow response to keystrokes. There is no problem in other applications. The problem goes away if I disconnect the external display. The problem does not go away if I switch from WiFi to a hardwired Ethernet connection. I had thought this might be the monitor's shielding problem interfering with WiFi but no, it happens without WiFi. Truly perplexing!

  • Presuming you've tried View > Adaptive Quality in the Screen Sharing app? – py4on Feb 17 '17 at 19:22
  • I hadn't but I see it's checked anyway. Should I try "Full Quality"? – Rob Steele Feb 17 '17 at 19:23
  • Go for it - should increase lag though not reduce it haha. Equally have you tried 3rd-party stuff with much more customisability regarding compression, exact colour etc (I'm thinking of VNCViewer Free which I use all the time for speedy Linux screen sharing). – py4on Feb 17 '17 at 19:25
  • Ha! VNCViewer fixes it! What on earth could make Screen Sharing not play nicely with an external monitor? – Rob Steele Feb 17 '17 at 21:04
  • It's Apple's homespun (read terrible) version of VNC which has multiple seemingly inexplicable issues. I ditched the ScreenSharing app for VNCViewer years ago. Only thing you might miss is forwarding clipboard contents into a session (or retrieving them seamlessly) and of course drag and drop with files. – py4on Feb 17 '17 at 21:05

Apple's implementation of VNC ScreenSharing often falls short, with significant lag regardless of whether Adaptive Quality is selected or not. A more robust 3rd-party solution like (the free) VNCViewer will provide you with fine-grained compression control, allowing workable VNC sessions over the tightest of bandwidth (e.g. through a shell tunnel to a remote server with really low upload speeds).

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