Keyboard, mouse, or external monitor not working on Mac
You plug an external keyboard, mouse, or monitor into your Mac and nothing happens, or the screen stays black. Before assuming a piece of hardware has failed, work through a few simple checks.
What to check
Check the cable and the port it's plugged into
Unplug the cable and reconnect it, ideally into a different USB-C or USB port if your Mac has more than one. Also check that the cable isn't visibly damaged and that it's seated firmly at both ends.
Check batteries and pairing for Bluetooth devices
A wireless keyboard or mouse that suddenly stops responding often simply has flat batteries. Go to System Settings → Bluetooth and check whether the device shows up as connected in the list — if not, pair it again.
For an external monitor, open System Settings → Displays
If the monitor is plugged in but the Mac doesn't seem to see it, open System Settings → Displays and check whether it shows up as available there. Sometimes you need to hold the monitor's "detect displays" button or switch its input source.
Test the device on a different port or a different computer
If you can, try plugging the same keyboard, mouse, or monitor into a different port or a different computer. It's a quick way to work out whether the problem lies with the device itself, the cable, or the Mac's port.
Why it's worth checking things one at a time
Problems with external devices rarely mean the Mac itself has failed — most often it's a loose connection, a flat battery, or a signal that wasn't detected properly. Working through the checks in order lets you rule out the obvious causes quickly.
When it's a job for IT
- The device doesn't work on any port or with a different computer, suggesting it's actually faulty.
- The port on the Mac looks physically damaged or doesn't respond to any device at all.
- The equipment is company property and needs a replacement or a warranty claim.
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