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iPerf3 vs Flent: catalog facts
iPerf3	Flent
Free Free and open source under the BSD 3-Clause licence, developed at ESnet and Lawrence…	Free Free to download and use, with the source published on GitHub.
Windows, macOS, Linux, Command line	Linux, Command line
Measures the link between two machines you own, not a public server TCP, UDP and SCTP with tunable windows, streams and packet sizes	Repeatable aggregate tests built on netperf and iperf Interactive GUI and extensive plotting
Command line only Not backwards compatible with the original iperf	Needs netperf or iperf and a test server on the other end Aimed at technical users rather than a quick speed check
Downloadable app	Downloadable app
Open source	Closed source
License: BSD-3-Clause	License not stated
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.