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How to Check Ethernet Cable Speed on Windows, macOS, Linux

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How to Check Ethernet Cable Speed on Windows, macOS, Linux

This guide shows you how to check the actual link speed of your Ethernet connection on Windows, macOS, and Linux. You’ll see the negotiated speed between your computer’s network port and the device it’s plugged into (router, switch, or modem), which tells you if you’re getting the full gigabit (or faster) connection you’re paying for. No extra software is needed—just a few clicks or commands.

What You’ll Need

  • A computer with an Ethernet port (or a USB-to-Ethernet adapter).
  • An Ethernet cable connected between your computer and a network device (router, switch, or modem).
  • Administrator rights on Windows (to view adapter details), but not required on macOS or Linux.

Step-by-Step

Windows 10 / 11

  1. Press Windows + R, type ncpa.cpl, and press Enter. This opens the Network Connections window.
  2. Find your Ethernet adapter (it may be labeled “Ethernet” or “Ethernet 2”). Right-click it and select Status.
  3. In the Status dialog, look for the Speed field. It will show something like 1000/1000 (Mbps) for gigabit, or 100/100 (Mbps) for Fast Ethernet.
  4. Click Details to see additional info like the link-local address, but the Speed field is what you need.
  5. If the Speed shows a lower value than expected (e.g., 100 Mbps on a gigabit network), that indicates a cable or port issue.

macOS (Ventura and later)

  1. Click the Apple menu () and select System Settings.
  2. Go to Network in the sidebar. If you’re connected via Ethernet, you’ll see a green dot next to “Ethernet”.
  3. Click on Ethernet to see the connection details. The Speed is displayed directly—look for something like 1000baseT (gigabit) or 100baseTX (Fast Ethernet).
  4. If you don’t see it, click Details next to the connection, then look under the Hardware tab. The speed is shown as “Speed” (e.g., 1000 Mb/s).

Linux (using terminal)

  1. Open a terminal window.
  2. Type ethtool eth0 (replace eth0 with your Ethernet interface name—find it with ip link or ifconfig -a).
  3. Look for the line Speed. It will show something like 1000Mb/s for gigabit, or 100Mb/s for Fast Ethernet.
  4. If ethtool is not installed, you can use sudo apt install ethtool (Debian/Ubuntu) or sudo dnf install ethtool (Fedora).
  5. Alternatively, check with cat /sys/class/net/eth0/speed—this prints the speed in Mbps (e.g., 1000).

Common Mistakes

  • Confusing link speed with internet speed: The link speed is between your computer and the router, not your internet connection. A 1000 Mbps link doesn’t mean you get 1000 Mbps from your ISP.
  • Using the wrong interface name on Linux: Many systems use enp3s0 or ens33 instead of eth0. Always check with ip link first.
  • Looking at Wi-Fi status: If you’re also connected to Wi-Fi, you might accidentally check the Wi-Fi adapter’s speed instead of Ethernet. Make sure you select the correct adapter.
  • Assuming the cable is gigabit-rated: Cat5 cables (not Cat5e) only support 100 Mbps. If you have a gigabit connection, you need at least Cat5e.

Tips

  • Check both ends: The link speed is determined by the slowest component—your computer’s port, the cable, or the router/switch port. If you see 100 Mbps, try a different cable or port to isolate the issue.
  • Update drivers: On Windows, outdated network drivers can sometimes force a lower speed. Check the manufacturer’s website for the latest driver.
  • Use a known-good cable: If you’re troubleshooting, test with a cable you know works at gigabit speeds.
  • Look for LEDs: Many Ethernet ports have LEDs that indicate speed (e.g., green for gigabit, amber for 100 Mbps). The color varies by manufacturer, so check the port’s manual.

Troubleshooting

  • Speed shows 10 Mbps: This usually indicates a faulty cable or a very long cable (over 100 meters). Try a shorter, known-good cable.
  • Speed shows 100 Mbps but you expect gigabit: Check the cable category (Cat5e or higher), and verify that the router/switch port supports gigabit. Also, try a different port on the switch.
  • No Ethernet connection at all: Ensure the cable is firmly plugged in on both ends. Try a different port on the router. If using a USB adapter, try a different USB port.
  • On Linux, ethtool shows “Speed: Unknown!”: This can happen with some USB adapters. Try sudo ethtool eth0 (with sudo) to get more info, or check the driver with lspci -k.
  • On macOS, the Speed field is missing: If you’re using a USB-to-Ethernet adapter, the system may not display the speed in System Settings. Use system_profiler SPNetworkDataType in Terminal to see the link speed.

Frequently Asked Questions

What is a good Ethernet link speed?

For most home networks, 1000 Mbps (gigabit) is standard. If you have a gigabit router and a Cat5e or better cable, you should see 1000 Mbps. If you see 100 Mbps, your network is limited to Fast Ethernet speeds.

Does a higher link speed mean faster internet?

Not necessarily. The link speed is the maximum rate between your computer and the router. Your actual internet speed is limited by your ISP plan. A gigabit link is useful for local file transfers and streaming, but if your internet plan is 100 Mbps, you won’t get more than that from the internet.

Can a bad Ethernet cable cause slow internet?

Yes. If a cable is damaged or not properly shielded, it can cause packet loss, which slows down your connection. A cable that is only Cat5 (not Cat5e) will limit you to 100 Mbps, even if your router and computer support gigabit.

How do I know if my Ethernet port is gigabit?

Check the link speed as described above. If it shows 1000 Mbps, your port is gigabit. You can also check the specifications of your computer or motherboard online.

Why does my Ethernet speed show 100 Mbps but I have a gigabit plan?

This is likely due to a cable that is not rated for gigabit (Cat5 or older), a faulty cable, or a router/switch port that is only Fast Ethernet. Try a different cable and port to isolate the issue.

Can I force a higher link speed?

In some cases, you can manually set the speed in the adapter settings (e.g., in Windows, under Advanced Properties). However, forcing a speed that the cable or device doesn’t support can cause connection drops. It’s better to fix the underlying hardware issue.

Related

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