Skip to main content

What to do when the mouse cursor lags?

Updated

Written for Synergy 3 (v3.7.2, and v3.8.2 where noted) and Synergy 1 (v1.21.4, and v1.22.2 where noted), checked 7 October 2026.

Operating system: Windows, macOS, and Linux

The most common cause for a mouse cursor to lag is a bad Wi-Fi connection. You can check if this is the issue by doing a ping test. For the steps, see: How to do a ping test

The best solution is to use an ethernet cable. If your ethernet network is in another room, or you don't have one, then you could set up an ethernet network. If your computers don't have ethernet ports, you may need to purchase a USB ethernet adapter. For the options, see: How to fix lag issues by using an ethernet connection

Already on ethernet, or does the ping test look fine? Lag has other causes too, so work through the sections below, starting with the one for all operating systems. For the ping test steps, see: How to do a ping test

All operating systems

Set the log level back to Info on every computer. A higher log level can cause lag. The steps are in your product's section: Synergy 3 or Synergy 1

Lag started after you updated Synergy 1 or Synergy 3? Reset its settings on each computer, and if the lag is still there, reinstall it cleanly. An update that didn't install cleanly can cause lag, and a clean reinstall can fix it. On a work computer, ask your IT team first. These steps erase your settings, such as your screen layout, so note them before you start:

  1. Reset its settings.
  2. If the lag is still there, uninstall it, including its config files.
  3. Restart the computer.
  4. Install it again.

For the detailed steps on your operating system, see: Reinstalling or uninstalling

Cursor freezes after copying something large

Update every computer. Newer versions overhaul how the clipboard is sent, so a large copy no longer freezes the cursor. For the steps, see: Updating to a new version

The version that brought the fix is in your product's section: Synergy 3 or Synergy 1

  • Waits for the mouse to stop. The clipboard is sent once the mouse rests, not while you move it.
  • Sent in small pieces. Mouse and keyboard input isn't stuck behind it.
  • 128 MB size limit by default. Earlier versions allowed only a few MB.
  • Images go as compressed files, never raw pixels. More formats are read, such as PNG, JPEG and WebP.
  • You can see it. An icon shows while a clipboard is sent or received, and a warning shows if one is over the limit.

Windows

Lag, or the whole computer freezing for a moment? Lower the priority of synergy-core.exe, the process that shares your keyboard and mouse in Synergy 1 and Synergy 3. This needs an administrator account. On a work computer, ask your IT team. Do this on each of your Windows computers:

  1. Press Ctrl+Shift+Esc to open Task Manager.
  2. If Task Manager shows only a short list of apps, click More details.
  3. Click Details.
  4. Right-click synergy-core.exe.
  5. Choose Set priority.
  6. Click High.
  7. Click Change priority.

Each time synergy-core.exe starts again, such as when you change a setting or restart the computer, it goes back to Realtime, so repeat these steps if the lag comes back.

Why this helps: synergy-core.exe asks Windows for Realtime, the highest priority there is. At Realtime it can hold up the parts of Windows that handle the mouse, keyboard and disk, and on some computers the whole computer freezes for a moment. At High it still runs ahead of everyday apps.

Linux

Linux computer on Wi-Fi? The best fix is an ethernet cable. For the options, see: How to fix lag issues by using an ethernet connection

If that isn't possible, turn off Wi-Fi power saving on that computer. Its Wi-Fi then uses a little more battery. These steps are for NetworkManager, which most desktop Linux distributions use:

  1. Open a terminal.
  2. Run the following command, which turns off power saving for every Wi-Fi network:
    printf '[connection]\nwifi.powersave = 2\n' | sudo tee /etc/NetworkManager/conf.d/wifi-powersave-off.conf
  3. Run the following command to restart NetworkManager (the Wi-Fi may drop for a moment):
    sudo systemctl restart NetworkManager

Why this helps: to save power, the Wi-Fi adapter dozes between bursts of traffic, and anything sent to it waits until it wakes. That's why the cursor lags most when you first move onto that computer and smooths out while you keep moving it, and why a ping to that computer can be slow while a ping from it looks fine. To see this on a ping test, run the ping on another of your computers and ping the Linux computer. For the ping test steps, see: How to do a ping test

To turn power saving back on:

  1. Run the following command to delete the file:
    sudo rm /etc/NetworkManager/conf.d/wifi-powersave-off.conf
  2. Run the following command to restart NetworkManager:
    sudo systemctl restart NetworkManager

macOS

Mac on Wi-Fi? The best fix is an ethernet cable, or a Thunderbolt cable between two Macs. For the options, see: How to fix lag issues by using an ethernet connection

AWDL (Apple Wireless Direct Link), the wireless link behind AirDrop, Handoff and AirPlay, can interrupt a Mac's Wi-Fi every few seconds, mostly while one of those features is in use. It holds up only Wi-Fi, so once the Mac connects to your other computers over a cable, you can leave AWDL on and keep those features.

Have to stay on Wi-Fi? Try putting your Wi-Fi network on the channel AWDL uses. This helps only while the Mac is connected to your 5 GHz network, not a 2.4 GHz or 6 GHz one. To check, hold down Option and click the Wi-Fi icon in the menu bar: the channel and band show below your network's name. If the Mac is on another band, use a cable or the quick fix below instead.

To change the channel:

  • On a work network, ask your IT team. A cable may be the easier request, since Apple advises IT teams to keep channels 149 and 153 free in rooms where AirPlay to an Apple TV is used a lot.
  • On your own router, if you know how to change its settings, set its 5 GHz network to channel 149, or to channel 44 if the lag stays or your router doesn't offer 149.

If neither channel stops the lag, your Wi-Fi gets slower, or AirPlay to an Apple TV gets less smooth, set the channel back to automatic.

Quick fix: turn off AWDL. This stops the stutter, but only until macOS turns AWDL back on, which it keeps doing: after the Mac sleeps, Wi-Fi is switched off and on, or the Mac restarts, and whenever AirDrop, Handoff or AirPlay ask for it. AirDrop won't work while AWDL is off. Turning AWDL off needs an administrator account, so on a work Mac, ask your IT team.

Synergy 3 (v3.7.2 and later) can turn AWDL off for you from its AWDL warning. For the steps, and how to hide the warning, see the Synergy 3 section: AWDL warning on a Mac

In any version of Synergy 1 or Synergy 3, turn AWDL off with Terminal:

  1. Open the Terminal app.
  2. Run the following command:
    sudo ifconfig awdl0 down
  3. Enter your Mac password when Terminal asks for it. Nothing shows while you type it.

Each time macOS turns AWDL back on, the stutter can come back too, so turn AWDL off again. Unofficial tools exist that keep AWDL off by turning it off every time macOS turns it on. They are temporary workarounds and may break between macOS updates.

Why this helps: AWDL shares the Wi-Fi adapter with your network connection. While AirDrop, Handoff or a similar feature is in use, every few seconds it takes the adapter over to its own channel for a moment, to look for nearby Apple devices, and everything else on that adapter waits, so the mouse and keyboard stutter. AWDL usually works on channel 149; in most of Europe, and wherever 149 isn't allowed, it uses channel 44. When the Mac is connected to a network on that channel, the adapter may not need to switch at all. The lag usually shows on a Mac you control with another computer's keyboard and mouse, not the one sharing its keyboard and mouse. On a ping test, the stutter shows as ping spikes: now and then, one reply takes far longer than the rest. For the ping test steps, see: How to do a ping test

AWDL isn't something Synergy 1, Synergy 3 or any other app can support or avoid. It is part of macOS and shares the Wi-Fi radio with your network connection; macOS decides when it runs, and only your router can choose the Wi-Fi channel. It makes other network apps stutter too, such as game streaming.

Still lagging, or on ethernet? Turn off Handoff on the Mac to see whether it's the cause. While Handoff is off, Universal Control, Sidecar without a cable, and copy and paste between your Apple devices stop working.

  1. Click the Apple menu at the top left of the screen.
  2. Choose System Settings.
  3. Click General in the sidebar.
  4. Click AirDrop & Continuity, or AirDrop & Handoff if your Mac shows that instead.
  5. Turn off Allow Handoff between this Mac and your iCloud devices.

If the lag doesn't change, turn Handoff back on.

Lag stopped, but you need Handoff? Turn Handoff back on, and turn off copy and paste in Synergy 1 or Synergy 3 instead. Handoff keeps working, but copying on one of your computers and pasting on another through Synergy 1 or Synergy 3 stops working. On a work computer, ask your IT team first. The steps are in your product's section: Synergy 3 or Synergy 1

Why this helps: with Handoff on, what you copy on your iPhone, iPad or another Mac also lands on this Mac's clipboard. Synergy 1 and Synergy 3 then send it on to your other computers, and the cursor can pause while this Mac fetches the copy from the device it came from. With copy and paste turned off, Synergy 1 and Synergy 3 don't fetch what's on this Mac's clipboard, so a copy from another device no longer pauses the cursor.

Bitdefender or another antivirus app on the Mac? On a work Mac, ask your IT team first. Then check whether the antivirus app is the cause:

  1. Check that the antivirus app allows Synergy 1 or Synergy 3. The antivirus app's help explains how.
  2. If the lag is still there, uninstall the antivirus app.
  3. Check whether the lag has stopped.
  4. Install the antivirus app again.

If the lag stopped while it was uninstalled, ask the antivirus app's maker how to stop it slowing down Synergy 1 or Synergy 3.

What follows depends on your product: Synergy 3 or Synergy 1

Synergy 3

Log level

On every computer:

  1. In the sidebar, under Advanced, click Troubleshooting.
  2. Set Log level to Info (instead of Debug).

Cursor freezes after copying something large

Update every computer to Synergy 3 (v3.8.2 and later). The clipboard size limit was 4 MB in earlier versions.

AWDL warning on a Mac

In Synergy 3 (v3.7.2 and later), while its AWDL warning is showing:

  1. On the Screen layout, click Turn off AWDL in the AWDL warning.
  2. Enter your Mac password when macOS asks.

Each time macOS turns AWDL back on, the warning comes back unless you've hidden it. All Synergy 3 can do is turn AWDL off for you, and macOS turns it back on.

Once the lag has stopped, click Don't warn about AWDL in the warning if it's still showing. This hides the warning, and its Turn off AWDL button, for good on that Mac, so if the lag comes back later, use the Terminal steps in the macOS section. The warning checks only that AWDL is on and that the Mac's main connection is Wi-Fi, so it can stay after a channel change, or when a cable joins only your computers and the Mac still reaches the internet over Wi-Fi.

Turning off copy and paste

  1. In the sidebar, under User, click Copy & paste.
  2. Turn off Text and image copy and paste.

Synergy 1

Log level

On every computer:

  1. Open Preferences (in the Edit menu on Windows and Linux, or the Synergy menu on macOS).
  2. Click the Logs tab.
  3. Set Level to Info (instead of Debug or Verbose).
  4. Click Save.

Cursor freezes after copying something large

Update every computer to Synergy 1 (v1.22.2 and later). The clipboard size limit was 3 MB in earlier versions.

Turning off copy and paste

On your server computer:

  1. Click Configure Server.
  2. Click the Advanced tab.
  3. Clear Enable clipboard sharing.
  4. Click OK.

Related to

Related articles