You connect your external display and your MacBook ignores it completely. The screen stays blank, or Finder does not show the second display in the arrangement. Sometimes it worked yesterday, sometimes it has never worked. Either way, this is fixable in most cases.
TL;DR
Hold Option + F2 (or open System Settings > Displays) and click Detect Displays. If that does not work, restart with the cable plugged in.
First: check the cable and adapter
Most external display failures are cable or adapter issues, not software. Try a different cable if you have one. If you are using a USB-C or Thunderbolt adapter, try a different port on the Mac — not all USB-C ports support video out on every Mac model. Specifically:
- On MacBooks with multiple USB-C ports, only the Thunderbolt ports (those with the lightning bolt icon) support external displays.
- USB-C hubs vary in quality. A cheap hub may not reliably pass video signal.
Detect Displays
Open System Settings > Displays. Hold Option and a Detect Displays button will appear. Click it. This forces macOS to poll all connected display ports.
Reset the display connection
Unplug the cable from the Mac (not the display), wait 10 seconds, plug it back in. If you are using a hub or dock, unplug the dock entirely, wait 30 seconds, reconnect it. This often resolves detection issues caused by the cable being connected before the Mac is fully booted.
Restart with the display connected
This sounds trivial, but it works: shut your Mac down completely, leave the display cable connected, and power on. On some Macs, the display detection logic runs at startup and handles cases that live detection misses.
Check display resolution settings
If the display is detected but the image looks wrong (blurry, wrong size, black bars), go to System Settings > Displays and select your external display. Make sure the resolution matches the display native resolution. Choose “More Space” only if your display supports HiDPI at that size.
Reset NVRAM (Intel Macs)
On Intel-based Macs, NVRAM stores display and graphics settings. To reset it, shut down, then press the power button and immediately hold Option + Command + P + R for about 20 seconds. Release and let the Mac boot normally.
On Apple Silicon Macs
Apple Silicon (M1, M2, M3, M4) Macs have no NVRAM reset in the traditional sense. If you have a Mac Mini or Studio, disconnect power for 30 seconds before reconnecting the display. For MacBooks, try a full shutdown and reconnect rather than sleep-wake.
Check for macOS updates
External display bugs appear in new macOS releases and are usually patched quickly. Go to System Settings > General > Software Update and install any pending updates before assuming the problem is hardware.
If none of this works
Test the display with a different computer or device. If the display works elsewhere, the issue is with the Mac, cable, or adapter. If the display does not work with anything, the display itself may be faulty. If the Mac shows video from one port but not another, the port may have an issue worth discussing with Apple Support or an Apple Authorised Service Provider.