iPerf3 is a network throughput tool used to measure the performance of the network your Mac is using. Here’s how to use it in the macOS Terminal app.
iPerf (sometimes simply called “iperf”) is a UNIX memory, network throughput, and bandwidth tool first developed at the NCSA of the University of Illinois. iPerf is a fully compatible rewrite of the older Test TCP (ttcp) app originally written at the US Army’s Ballistic Research Lab for DARPA in around 1983.
There are also modern versions for Windows and Linux.