Measure the Speed Between Two of My Machines
An internet speed test says nothing about the link between your Mac and your NAS. iperf3 does. Here is how to measure it with Netutilus for Mac and read the result.
Download on the Mac App Store ↗
free to download · macOS 14.6 or later
Speed Test measures your connection to the internet, which your provider limits. To know what your own network carries, between this Mac and a NAS or another computer, measure between them with iperf3, part of Netutilus Pro.
1. Start a server on the other machine
Install iperf3 there (it’s in most package managers, and on many NAS systems) and run:
iperf3 -s
It waits for a test on port 5201. Netutilus is only the client, so the server has to be the other machine.
2. Run the test
In iperf3, click Add Server, enter the other machine’s address, and click Run. It measures upload, then download.
3. Compare with what the link can do
- Gigabit Ethernet carries about 940 Mbit/s in practice.
- Wi-Fi carries much less than its link rate: about half of the TX Rate Wi-Fi Analyzer shows is typical.
Far below that means something on the way is slower than you think: an old cable or switch port running at 100 Mbit/s, a weak signal, or a busy NAS disk.
4. Narrow it down
- Run once over Wi-Fi, then once over a cable. The difference is your Wi-Fi.
- Run from different rooms, or with the Mac near the router.
- Switch the server’s Protocol to UDP with a target bitrate to see jitter and lost datagrams, which matter for calls and streaming.
History keeps every run, so you can compare before and after a change.
Related
Run it on your own network
Netutilus puts every network tool in one app. Free to download; Pro is a one-time purchase, never a subscription.
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