Fix the "USB Devices Disabled" or "USB Accessories Disabled" alert

Why it happens

Each USB port can only give out a set amount of power. When a device, such as a portable hard drive or a hub full of gadgets, asks for more, macOS cuts power to protect the Mac and shows this alert. It's a safety step to stop anything getting damaged.

How to fix it

1. Unplug the device you connected just before the alert appeared. If you're not sure which one, unplug everything from that port or hub.

2. Plug the device in again, this time into a different port on the Mac.

3. If it was on a hub or dock, connect it straight to the Mac instead. Hubs share one port's power between everything on them.

4. If your hub came with its own power adapter, plug that in. A powered hub feeds hungry devices from the wall instead of from your Mac.

5. Plug your other devices back in one at a time. If the alert returns when one goes in, that's the device asking for too much.

Still not fixed?

1. Some big portable drives need more power than one port gives. Use the drive's own power adapter if it has one, or the cable that came with it.

2. Try a different cable. A damaged or cheap cable can short and trigger the alert even with a device that normally works.

3. Restart your Mac with everything unplugged, then connect devices one by one. This clears the cut-off on every port.

4. Test the device on another computer if you can. If it fails there too, the device or its cable is faulty, not your Mac.

5. If the alert appears with nothing plugged in, or one port always fails, the port itself may be damaged. That's a hardware problem, so contact Apple Support or a repair shop.