Is Your USB-C Cable Slow? Check USB Speed on Mac
To check USB speed on a Mac, hold Option, click the Apple menu, choose System Information and click USB. Select the device and read the speed it connected at. A USB 3 drive showing 480 Mb/s is running at USB 2 speed, and the cable is the usual cause. Use a 10 Gb/s cable, straight into the Mac.
TL;DR
- 480 Mb/s = USB 2. Fine for keyboards and mice, painfully slow for SSDs (under 60 MB/s at best).
- 5 / 10 Gb/s = USB 3 Gen 1 / Gen 2. What most external SSDs want.
- 40 Gb/s and up = USB4 or Thunderbolt.
- Many USB-C charge cables carry only USB 2 data. They look identical.
- Check it: System Information › USB,
ioregin Terminal, or FavTray System, which warns you when a fast device is stuck at USB 2 speed.
How do you check the USB speed of a device on a Mac?
- Hold Option and click the Apple menu, then choose System Information. (Without Option: Apple menu › System Settings › General › About › System Report.)
- In the sidebar, under Hardware, click USB. For a Thunderbolt or USB4 dock, check Thunderbolt/USB4 too.
- Select your device in the tree. Its details include the speed it’s connected at.
Compare that with what the device is rated for. An SSD sold as “10 Gb/s” that shows 480 Mb/s is running at about 5% of its rated speed.
How do you check USB speed in Terminal?
ioreg lists every USB device with its negotiated speed and the USB version it was built for:
ioreg -p IOUSB -l -w0 | grep -E '"USB Product Name"|"Device Speed"|"bcdUSB"'Read the numbers like this:
Device Speed | Negotiated speed | Name |
|---|---|---|
| 0 | 1.5 Mb/s | USB 1 low speed |
| 1 | 12 Mb/s | USB 1 full speed |
| 2 | 480 Mb/s | USB 2 |
| 3 | 5 Gb/s | USB 3 Gen 1 |
| 4 | 10 Gb/s | USB 3 Gen 2 |
| 5 | 20 Gb/s | USB 3 Gen 2x2 |
bcdUSB is the USB version the device was designed for, in hex: 0x0200 is USB 2, 0x0300 and up is USB 3, 0x0400 is USB4. A device with bcdUSB of 0x0300 or higher and Device Speed of 2 is a USB 3 device running at USB 2 speed. Hubs are the exception; they report their own quirks.
On macOS 26, the old system_profiler SPUSBDataType returns nothing; it was replaced by SPUSBHostDataType, which is why ioreg is the more reliable Terminal route.
Why is my USB-C device running at USB 2 speed?
The connection runs at the speed of its slowest part. In order of likelihood:
- The cable. USB-C is just the plug shape. Many cables, including the charge cables that ship with a lot of laptops and phones, carry only USB 2 data at 480 Mb/s, even when they charge at high wattage. They look the same as a 10 Gb/s cable.
- A hub, dock or adapter in between. A cheap hub, a monitor’s built-in USB ports, or a USB-A adapter can drop everything behind it to USB 2.
- The port. Some displays and older Macs have ports limited to USB 2 or 5 Gb/s.
- A 20 Gb/s drive. Macs don’t support USB 3.2 Gen 2x2, so drives rated for 20 Gb/s connect at 10 Gb/s. That’s expected, not a fault.
- A bad connection. A loose or damaged plug can fall back to a slower speed. Reseat it or try the other orientation.
The quick test: plug the device straight into the Mac with the cable it came with, then check the speed again.
What USB speed do you need?
| Device | Enough | Notes |
|---|---|---|
| Keyboard, mouse, audio interface | USB 2 (480 Mb/s) | USB 2 is not a problem here |
| External hard drive (spinning) | 5 Gb/s | The disk is slower than the link |
| External NVMe SSD | 10 Gb/s | Or USB4 / Thunderbolt for NVMe enclosures that support it |
| Dock with displays and Ethernet | Thunderbolt or USB4 (40 Gb/s) | Displays take a big share of the link |
| Capture cards, 4K webcams | 5 Gb/s or more | Many fall back to lower resolution at USB 2 |
When you buy a cable for data, look for a printed speed (10 Gb/s, 20 Gb/s, 40 Gb/s), a USB4 or Thunderbolt logo, or a spec sheet that states the data rate, not just the wattage.
How can your Mac warn you about a slow USB connection?
FavTray’s System tool has a USB & Thunderbolt section that lists connected devices with the USB version each was designed for and the speed it actually connected at. When a USB 3 device has connected at USB 2 speed or below, it shows a USB 2 speed warning on that device, which is usually your cue to change the cable or hub. It reads the same data as ioreg, without Terminal and without any extra permission.
The same window covers storage reads and writes per disk and the SSD’s SMART status, so you can see whether a copy is slow because of the link or the drive. If the problem is space rather than speed, what’s eating your Mac’s disk walks through the usual suspects.
Free vs Pro: the USB & Thunderbolt list and the USB 2 speed warning are free. Pro, a one-time Lifetime licence, adds disk reads and writes by app, longer history and export.
Sources (checked 28 September 2026): System Information and ioreg on a MacBook running macOS 26.6.2; the Device Speed codes are the IOUSBHost values FavTray reads; Apple Community thread on SPUSBDataType missing in macOS 26.
Frequently Asked Questions
How do I check USB speed on a Mac?
Hold Option, click the Apple menu and choose System Information, then click USB in the sidebar. Select your device and read its speed line: 480 Mb/s is USB 2, 5 Gb/s is USB 3 (Gen 1), 10 Gb/s is USB 3 Gen 2. That's the speed the device actually connected at, which is limited by the slowest part of the chain: port, cable, hub or device.
Why is my USB-C SSD so slow on my Mac?
The most common reason is a USB-C cable that only carries USB 2 data (480 Mb/s), such as the charge cables that come with many laptops and phones. Other causes are a USB 2 hub or dock in between, a USB-A adapter, or a drive rated for USB 3.2 Gen 2x2 (20 Gb/s), which Macs run at 10 Gb/s. Try the drive's own cable, plugged straight into the Mac.
Do all USB-C cables transfer data at the same speed?
No. USB-C is only the connector shape. A USB-C cable can carry USB 2 (480 Mb/s), 5, 10 or 20 Gb/s, USB4 at 40 or 80 Gb/s, or Thunderbolt, and many charge cables are USB 2 only. Look for the speed printed on the cable or its packaging, or a Thunderbolt or USB4 logo.
Can I check USB speed in Terminal?
Yes. Run ioreg -p IOUSB -l -w0 | grep -E '"USB Product Name"|"Device Speed"|"bcdUSB"'. Device Speed is a code: 2 means 480 Mb/s (USB 2), 3 means 5 Gb/s, 4 means 10 Gb/s and 5 means 20 Gb/s. bcdUSB is the USB version the device was designed for, so a device with bcdUSB 0x0300 or higher at Device Speed 2 is running below its rated speed.
Does a USB 2 cable slow down charging?
Not necessarily. Charging power and data speed are separate. Many USB 2 data cables still charge at high wattage, which is why a cable can charge your Mac quickly and still copy files slowly.