Why is my gigabit internet limited to around 90 Mbps?

Check every device between the computer and modem or router. Some older routers, switches, powerline adapters, and wall wiring only support 100 Mbps, even if the router or internet plan supports 1,000 Mbps. Powerline adapters in particular can be limited by the electrical wiring in the building.

If you’re using Wi-Fi, the limitation could be the wireless standard, distance, interference, or being connected to the 2.4 GHz band. For testing, connect the computer directly to a gigabit-capable router port with a good Ethernet cable, then check the adapter’s negotiated link speed. It should report 1.0 Gbps, not 100 Mbps.

A speed that consistently tops out around 90–100 Mbps usually means one part of the connection negotiated a 100 Mbps link instead of gigabit. Check that the Ethernet cable is fully connected and replace it with a known-good Cat5e or better cable. A damaged connector or wire can cause the devices to fall back to 100 Mbps.

The 10% figure in Resource Monitor isn’t necessarily a speed limit. It may be showing usage relative to the network adapter’s negotiated capacity. Run a proper speed test and verify your subscription speed too, since a gigabit-capable local connection cannot exceed an internet plan that is actually rated at 100 Mbps.