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Mac Not Recognizing USB Drive

On an Apple silicon laptop this is often the Allow accessory prompt, not a broken stick. On any Mac it can also be a cable that doesn’t do data, or a port that’s already busy.

About 7 minutes · Tick the steps as you go

1. Allow the accessory

Apple silicon laptops ask before a new USB stick, Thunderbolt enclosure, or SD card can talk to the Mac. If the Mac is locked, you won’t get a useful prompt until you unlock it.

Click Don’t Allow and the Mac will pretend the thing isn’t there. Charge can still work, which is confusing — the light comes on, Finder stays empty. Plug it in again and you should be asked a second time.

Unlock the Mac, plug the drive in, click Allow if a sheet appears. If the Mac sat locked for several days, unlock it even for a stick you already trusted. It can ask again. System Settings > Privacy & Security > Accessories. “Ask for new accessories” is the sane default. “Always allow” is how you stop thinking about it on a desk you control.

Closed-lid laptop on a dock: allow the display, mouse, and keyboard first. Other accessories can follow without opening the lid. If you never allowed the dock, nothing downstream will show up.

2. Prove the cable carries data

Phone-charger cables are the silent killer here. The enclosure LEDs happily light up. The Mac never sees a storage device.

Plug into the Mac itself, not a dock, for the first test. Try a second cable you know you’ve copied files through. Try a second port. Some left/right ports on a laptop behave differently under load.

3. System Information doesn’t lie

Option-click the Apple menu > System Information. USB, or Thunderbolt / USB4. You want the enclosure or the stick named in that tree.

If it never appears there, Disk Utility cannot help yet. Go back to cables, power, and the Allow prompt. If it appears there but not in Disk Utility, jump to Drive Missing From Disk Utility and the Show All Devices view.

4. Still nothing

Test the stick on another computer if you have one. A device that is invisible everywhere is not waiting on a hidden macOS checkbox.

Apple’s pages, if you want them: Allow USB and other accessories to connect

I wrote these lists from the same public Mac Help and Disk Utility notes everyone can read — in my own words, with the order I actually use. Apple’s pages are linked above if you want the official version.

Still stuck?

If this list didn’t get the drive back, write to me.

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