iPerf3 is a command-line tool for measuring network performance between two computers. Running a test can be done by starting the iPerf3 server on one device with iperf3 -s and then connecting with the client from another device iperf3 -c {server-ip-or-host}.

# First device - start server
iperf3 -s
 
# Second device - connect with client
iperf3 -c {server-ip-or-host}
 
# Client output
Connecting to host 100.119.22.54, port 5201
[  5] local 100.120.170.40 port 37072 connected to 100.119.22.54 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  1.88 MBytes  15.7 Mbits/sec    0    223 KBytes
[  5]   1.00-2.00   sec  2.48 MBytes  20.8 Mbits/sec   15    218 KBytes
[  5]   2.00-3.00   sec  2.17 MBytes  18.2 Mbits/sec    0    255 KBytes
[  5]   3.00-4.00   sec  2.17 MBytes  18.2 Mbits/sec    0    284 KBytes
[  5]   4.00-5.00   sec  2.17 MBytes  18.2 Mbits/sec   19    215 KBytes
[  5]   5.00-6.00   sec  1.74 MBytes  14.6 Mbits/sec    0    235 KBytes
[  5]   6.00-7.00   sec  2.17 MBytes  18.2 Mbits/sec    0    246 KBytes
[  5]   7.00-8.00   sec  2.17 MBytes  18.2 Mbits/sec    0    251 KBytes
[  5]   8.00-9.00   sec  2.17 MBytes  18.2 Mbits/sec    0    251 KBytes
[  5]   9.00-10.00  sec  1.86 MBytes  15.6 Mbits/sec   15    191 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  21.0 MBytes  17.6 Mbits/sec   49             sender
[  5]   0.00-10.09  sec  20.5 MBytes  17.0 Mbits/sec                  receiver

Installing iPerf3

You can install iPerf3 on just about any device. See the home page for instructions for different operating systems or where to download the binary. In a nutshell, you can install iPerf3 with:

# Arch
pacman -S iperf3
# Debian/Ubuntu
sudo apt-get install iperf3
# Fedora
sudo dnf install iperf3
# Chocolatey
choco install iperf3
# Scoop
scoop install iperf3
# Brew
brew install iperf3

You can also clone the GitHub repo and build it directly. Alternative there is also a docker image available to use.

How iPerf3 works

iPerf3 works as a client/server application, so you need to install it on at least two devices.

One device will act as the server and the other device will act as the client.
The server will wait for a client to connect to it
Once the client connects, the client will begin sending data to the server

This means the device that acts as the client using the -c flag will be the one transmitting data to the server. If you want to reverse the test so the client receives data from the server, you can use the -R or --reverse flag

Using iPerf3

Test upload speed to server

# Server
iperf3 -s
# Client
iperf3 -c {server-ip-or-host}

Test download speed from server

Use the -R or --reverse flag

# Server
iperf3 -s
# Client
iperf3 -R -c {server-ip-or-host}

Test upload & download simultaneously

Use the --bidir flag to do a bidirectional test

# Server
iperf3 -s
# Client
iperf3 --bidir -c {server-ip-or-host}

Other useful flags

-p or --port - Specify the port to use
-i or --interval - Specify the interval to report bandwidth usage
-f or --format - Specify the format to use for reporting bandwidth usage (Kbits, Mbits, Gbits, Tbits)
-j or --json - Output the results in JSON format
-V or --verbose - Output more verbose information

Client specific options

-t or --time - Specify the time to run the test for

Server specific options

-D or --daemon - Run the server as a daemon

Test Network Bandwidth Between Devices with iPerf3