Windows iperf3

If you're needing to speed-test your internet service then you can use web-based speed testers, but they may not always give you accurate results. An alternative is using a tool called iperf3 to run a speed test against an iperf3 server that is hosted at your ISP.

Here is how to download and run iper3 on Windows and how to test single and multi-thread upload and download speeds. - This uses the Andrews & Arnold speed test server, which is only available to customers.

The version of iperf3 we have here is 3.13 from June 2023 - and is newer than the version that is hosted on the official iperf.fr website and so has a lot of bug fixes. - thanks to Mini for compiling this.

1)

Download File:Iperf-3.13-windows-x64.zip and save it to your computer, eg in your Downloads folder.

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2)

Right click on it, and select Extract all.

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3)

Open up the Command Prompt - Click Start then type cmd and click on the 'Command Prompt' icon.

4)

In the black box type: cd Downloads\iperf-3.13-windows-x64

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5)

Run an speed test by typing: iperf3.exe -c speedtest.aa.net.uk (you may need to click 'allow access' if a Windows Defender window pops up

By default, this will run a single-thread upload speedtest (sending traffic TO the speed test server). As you can see in the screenshot, the upload speed this line happens to get is just over 19Mb/s.

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Variations

There are variations you can do to test the speed as follows:

• Run a single-thread Download test: iperf3.exe -R -P1 -c speedtest.aa.net.uk
• Run a single-thread Upload test: iperf3.exe -P1 -c speedtest.aa.net.uk
• Run a 10-thread Download test: iperf3.exe -R -P10 -c speedtest.aa.net.uk
• Run a 10-thread Upload test: iperf3.exe -P10 -c speedtest.aa.net.uk

What to look for:

• The results should be near to the speed you'd expect for your line.
• You may want to run the tests at different times of day so as to see if there is any peak-time congestio0n affecting you.
• Hopefully the single and multi-thread tests give similar results - if not, there may be some sort of problem.