I have Verizon Fios service nominally 100 down/100 up. I have two computers connected to the same router with Ethernet cables. They both have 1 Gbps Ethernet adapters. Using an online speed test, one is getting 82/82 and the other is getting 15/82. What could cause one computer to have such low download speeds?
Swap cables and see what happens.
This sounds like an application layer issue. Try a different browser or download an app dedicated to that function. I’ve never had much consistency on browser hosted tests.
Here is one from the Microsoft Store (signup required but is free) https://www.microsoft.com/en-us/p/speed-test-free-internet-speed-test-tools/9p3d31qdw2ws?activetab=pivot:overviewtab
Good luck.
any differences in firewall/anti virus software?
Was the other machine downloading something while speedtest was running?
try different router/switch port in case there is a bad connection/damaged/dirty pins in port?
Are both computers more or less the same? If it’s not a connection issue, it may be a packet size problem.
Are you testing both at the same time? Don’t do that. To be sure they aren’t interfering with each other try testing one with the other off or disconnected from the network.
Also, the speed can change based on the server you test against. It may not be the same server even if you’re testing at the same website.
You can checkout this site.
https://www.speedguide.net/sg_tools.php
Some systems come with poorly configured settings for the ethernet interfaces. I have used the analyzer and optimizer without any problems. But only up to Win 7 OS.