USB Device Not Recognized
How to fix a USB device that is not detected or keeps disconnecting
A USB device that is not recognized is usually caused by a bad connection, a power issue, or a missing driver. Before doing anything else, try a different USB port and a different cable if you have one. That alone fixes the problem about half the time.
If swapping ports and cables does not help, work through the steps below for your operating system.
- Unplug the USB device, wait 10 seconds, and plug it back in — try a port directly on the Mac rather than through a hub
- If you are using a USB hub, make sure it is a powered hub (has its own power adapter). Bus-powered hubs often cannot supply enough power for drives and some peripherals
- Open System Information — press Cmd + Space, type
System Information, and press Return - In the sidebar under Hardware, click USB and check whether your device appears in the list. If it does, the Mac sees the hardware but may not be mounting it (for drives) or loading the right driver
- For USB storage drives that appear in System Information but not in Finder, open Disk Utility (in Applications > Utilities). If the drive shows up in the sidebar, select it and click Mount. If it shows as unformatted or corrupted, Disk Utility can attempt a repair with First Aid
- Reset the USB bus by restarting your Mac. On Apple Silicon Macs, a restart is the equivalent of the old SMC reset
- Check for macOS updates — System Settings > General > Software Update. USB compatibility fixes ship in minor updates regularly
- If the device needs specific software (audio interfaces, printers, specialized peripherals), download the latest driver from the manufacturer's website. Many USB devices that worked on Intel Macs need updated drivers for Apple Silicon
Frequently Asked Questions
Why does my USB device work on one port but not another?▾
USB ports are not all equal. Front panel ports on desktops often have weaker power delivery than rear ports. Some ports are USB 2.0 and others are USB 3.0 — a device might need the higher power available on USB 3.0 ports. It is also possible that one specific port has a hardware fault or a disabled controller in the BIOS.
Is a powered USB hub necessary?▾
If you are connecting devices that draw significant power (external hard drives, audio interfaces, bus-powered docking stations), yes. A standard USB port provides 500mA (USB 2.0) or 900mA (USB 3.0). Daisy-chaining multiple devices through an unpowered hub splits that limited power among all connected devices, which often causes detection failures.
Will I lose data if I unplug a USB drive without ejecting?▾
Possibly. When you copy files to a USB drive, the operating system may cache writes and not flush them to the drive immediately. Pulling the drive without ejecting can result in corrupted files or a corrupted file system. Always eject or safely remove the drive first — it takes two seconds and prevents data loss.
What does "USB device descriptor failed" mean?▾
This error means the operating system tried to communicate with the USB device but could not read its identification data. It is usually a power issue, a bad cable, or a failing USB controller on the device itself. Try a different cable and port first. If the error persists across multiple computers, the device may be faulty.