Why is Ethernet slower than Wi-Fi?

When Ethernet tests slower than Wi-Fi, the wired link has almost always connected at 100 Mbps instead of 1 Gbps. A worn or old cable, a slow port, a cheap USB adapter or a power-saving driver setting can each cause it. The giveaway is a wired result that stops in the low 90s no matter what plan you pay for. Check the link speed your computer negotiated. If it says 100 Mbps, swap parts one at a time until it says 1 Gbps (1,000 Mbps).

Why a wired result tops out around 94 Mbps

Ethernet links agree on a speed when you plug in. Most home equipment supports 10, 100 and 1,000 Mbps, and some newer gear supports 2.5 Gbps or more. Both ends pick the fastest speed they and the cable can handle.

Gigabit Ethernet needs all four wire pairs inside the cable. 100 Mbps Ethernet uses only two. So if one wire in the other two pairs is broken, crushed or badly crimped, the link doesn't fail. It quietly falls back to 100 Mbps, and everything looks fine apart from the speed.

A 100 Mbps link can't deliver a full 100 Mbps of internet, because some of each packet is headers and acknowledgements. As a rule of thumb, a speed test over a 100 Mbps link lands at around 90–95 Mbps. If your Wi-Fi gets 300 and your cable gets 93, that's the pattern.

Check the negotiated link speed

This takes a minute, and it tells you whether the link is the problem before you buy anything.

Windows 11: Settings > Network & internet > Ethernet. Look for "Link speed (Receive/Transmit)". On Windows 10, go to Control Panel > Network and Sharing Center, click your Ethernet connection, and read "Speed".

macOS: Open Terminal and run ifconfig | grep media. A healthy gigabit link shows 1000baseT. 100baseTX means the link has dropped to 100 Mbps.

Linux: Run ethtool eth0, replacing eth0 with your interface name, and read the "Speed:" line. cat /sys/class/net/eth0/speed shows the same number.

Link speed shown	What it means
1.0 Gbps / 1000 Mbps / 1000baseT	The link is fine. Look at the other causes below
100 Mbps / 100baseTX	Something in the chain is limited to 100 Mbps
10 Mbps	A damaged cable or a failing port
2.5 Gbps or higher	A multi-gig link. The cable isn't the problem

Find the slow part in the chain

Your wired connection runs through several parts, and any one of them can force 100 Mbps. Swap one thing at a time and recheck the link speed after each change.

The cable. This is the most common cause. Try a different cable, ideally one marked Cat5e or Cat6 on the jacket. Plain Cat5 is rated for 100 Mbps. For which category to buy, see Cat5e vs Cat6. Also look for kinks, flattened sections under doors, a cable stapled to a skirting board, or a plug with a broken latch that sits loose in the port.

The wall socket or patch panel. If the cable runs through wall plates, the wiring in the wall may be the weak link. Test with a single cable plugged straight into the router. If that reaches 1 Gbps, the in-wall run or its sockets needs re-terminating.

The router or switch port. Try another LAN port on the router. Older or very cheap switches, some ISP routers' extra ports, and many powerline adapters are limited to 100 Mbps. If your cable passes through a small switch behind the TV, plug straight into the router to rule it out.

The adapter. Laptops without a built-in port depend on a USB or Thunderbolt dongle. Some cheap adapters and USB hubs are 100 Mbps only. A gigabit adapter in a USB 2.0 port is capped by that port's 480 Mbps maximum, shared with everything else on it. Check the adapter's listed speed, and plug it into a USB 3 or USB-C port directly rather than through a hub.

The driver and power settings. On Windows, open Device Manager, find the Ethernet adapter, and look at Properties > Advanced. Make sure "Speed & Duplex" is set to Auto Negotiation, not a fixed 100 Mbps. If the link keeps dropping or falling back, try turning off "Energy Efficient Ethernet" or "Green Ethernet", and update the driver from the computer or chip maker.

When the link says 1 Gbps but the test is still slow

If the negotiated speed is fine, the cable is doing its job. Compare like with like:

• Same device, same browser. A wired desktop with a VPN client, a busy antivirus or many browser extensions can test slower than a clean laptop on Wi-Fi. VPNs in particular cut speed.
• Same time. Run the Wi-Fi and wired tests back to back with the SpeedMetric speed test, not hours apart.
• The device itself. An old computer may not keep up with a fast connection, wired or not.

There's also one case where Wi-Fi winning is normal. On a plan faster than 1 Gbps, a recent Wi-Fi 6E or Wi-Fi 7 laptop near the router can beat a computer plugged into a 1 Gbps port. A gigabit link tops out a little under 1,000 Mbps after overhead, while the Wi-Fi link may run faster. In that case you need multi-gig ports, not a new cable.

Then confirm the fix

Once the link shows 1 Gbps, run two or three tests on the cable. A wired result should now match or beat Wi-Fi in the same room, and it should be steadier from run to run. If both connections are still well under your plan, the bottleneck is upstream of your computer. Read why a speed test can sit below the advertised rate, then work through the step-by-step debug path. If you were here for the opposite problem, see why Wi-Fi is slower than Ethernet.