Mac Screensaver Not Working? Here's Why

· Scanner Techs

You chose a screensaver, walked away, and came back to a black screen, or to your desktop exactly as you left it. Nearly always it’s one of a handful of causes, and most are a single setting. Here they are, most likely first.

1. The display turns off before the screensaver starts

This is the big one. The screensaver and the display each have their own timer, and if the display’s is shorter, the screen goes dark before the screensaver ever gets its turn. You’ll never see it, and nothing looks broken.

Open System Settings → Lock Screen and compare:

  • Start Screen Saver when inactive, and
  • Turn display off on battery when inactive / on power adapter when inactive.

The screensaver’s time has to be shorter. For example: screensaver after 2 minutes, display off after 10. If Start Screen Saver when inactive says Never, that’s your answer too.

2. Something is keeping the Mac awake

Apps can tell macOS “the user is busy, don’t dim the screen”, and while one does, the screensaver waits. The usual suspects:

  • a video playing, in a browser tab or an app, even one hidden behind other windows;
  • a video call: Zoom, Teams, Meet and the like keep the screen on for the whole call;
  • keep-awake apps such as Amphetamine, caffeinate, or StayUp, which exist to do exactly this;
  • presentation and screen-sharing apps.

To see exactly what’s holding it, open Terminal and run:

pmset -g assertions

Look for PreventUserIdleDisplaySleep in the list at the top. If it says 1, something is preventing it, and further down the output, the lines that mention it name the app or process responsible. Quit that app (or close the tab) and the screensaver can start again.

3. Something keeps nudging the Mac

The screensaver starts when there’s been no input for the set time, and “input” is broader than you’d think. A wireless mouse on a glossy or patterned desk can twitch on its own; a drawing tablet, game controller or some USB devices can send a steady trickle of events. If the screensaver works when you unplug or turn something off, that’s the culprit.

4. The one you chose isn’t the one that runs

If a different screensaver appears, or a third-party one shows black, the choice may not have been saved:

  • In System Settings → Screen Saver, click the one you want again and wait a moment before closing the window.
  • Screensavers from outside Apple sit lower down the gallery, under Other. If you can’t see them, press Show All.
  • If you installed a .saver file and it doesn’t appear at all, macOS may have blocked it the first time. Installing a .saver file walks through getting past that warning.

5. Your changes don’t seem to take effect

On recent macOS versions, third-party screensavers run inside a helper process called legacyScreenSaver, which can keep the old settings until it restarts. If you’ve changed a screensaver’s options and it still runs the old way, quit the helper so the next run starts fresh:

killall legacyScreenSaver

It’s harmless: macOS starts it again the next time the screensaver runs.

6. It starts, then stops straight away

A screensaver that appears and immediately vanishes is usually being woken by the same causes as above: a twitching mouse, a device sending input, or an app taking over the screen (a notification, a calendar alert, a call). Check those first. If it happens with every screensaver, including Apple’s, try a restart; if it’s only one third-party screensaver, it’s that screensaver.

Still nothing?

Test with one of Apple’s own, such as Flurry. If Apple’s screensaver doesn’t start either, the cause is the Mac’s settings or something keeping it awake, so go back to 1 and 2. If Apple’s works and yours doesn’t, the problem is that particular screensaver, and its maker is the one to ask.

For the full tour of the settings, see how to change your screensaver on macOS. And if you’re weighing the battery cost of leaving one on, we measured it.

All posts · Nap is our own collection of screensavers for the Mac. Install it and the first two days are free.