Flent
Flent is a free, open-source desktop tool for running repeatable network experiments, primarily to test for bufferbloat.
What Flent is
Flent is a free, open-source desktop tool for running repeatable network experiments, primarily to test for bufferbloat. It combines netperf and similar benchmarking utilities into predefined test runs, aggregates their results, and produces plots. Tests can capture metadata from local and remote hosts and keep it with plot data. Additional measurements can include CPU usage, WiFi, qdisc, and TCP socket statistics. Batch experiments let users automate testing regimes. Results can be saved as gzipped JSON or output as CSV, Org tables, and plots; plot files can use formats supported by matplotlib, including PNG, PS, PDF, and SVG. Most tests use netperf 2.6 or later, while some use iperf, and the applicable tool must be available in PATH. For UDP measurements, the documentation recommends irtt and says its server must run on target hosts. An interactive plot viewer is available. macOS installation instructions list PyQt5 and qtpy as optional GUI dependencies. The site lists installation options for Linux distributions, FreeBSD, and macOS. Flent supports active TCP, UDP, and ICMP testing.
Good
- Combines network tools into repeatable experiments
- Captures metadata and secondary measurements
- Automates test regimes with batch runs
- Exports results in several data and plot formats
Watch out
- Most tests require netperf 2.6 or later
- UDP measurements require an irtt server on target hosts
Who it suits
Flent suits people making network experiments who want repeatable test runs and aggregated plots, especially for bufferbloat testing. It is available for Linux and macOS, with installation options also listed for FreeBSD.
Verdict
Flent offers a free way to automate network tests and inspect combined results, with support for several measurement types and export formats. Users need the relevant benchmarking tools available for the tests they plan to run.
Plans and prices
From Flent's own pricing page, checked 4 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| Flent | Free | No paid plans or usage limits stated on the opened pages |
The facts
Each one read from Flent's own pages, with the date it was checked.
What it does
- Additional measurements
- It can collect CPU usage, WiFi, qdisc, and TCP socket statistics as secondary data series.checked 4 Oct 2026
- Automation
- Batch experiment runs can automate testing regimes.checked 4 Oct 2026
- Data capture
- It can capture metadata from local and remote hosts and store it with plot data.checked 4 Oct 2026
- Desktop GUI
- An interactive plot viewer is available, and the macOS installation instructions list PyQt5 and qtpy as optional GUI dependencies.checked 4 Oct 2026
- Intended users
- The project describes Flent as a tool for making network experiments more reliable and easier to perform.checked 4 Oct 2026
- Outputs
- Aggregated results can be saved as gzipped JSON or output as CSV, Org tables, and plots.checked 4 Oct 2026
- Plot formats
- Plots can be saved in formats supported by matplotlib, including PNG, PS, PDF, and SVG.checked 4 Oct 2026
- Purpose
- Flent wraps netperf and similar tools to run predefined network tests, aggregate results, and plot them, primarily to test for bufferbloat.checked 4 Oct 2026
- Repeatable tests
- It combines benchmarking tools into aggregate, repeatable test runs.checked 4 Oct 2026
- Supported installs
- The site lists installation options for Linux distributions, FreeBSD, and macOS.checked 4 Oct 2026
- Tools and dependencies
- Most tests use netperf 2.6 or later, while some use iperf; both tools must be available in PATH for the tests that use them.checked 4 Oct 2026
- UDP measurements
- The documentation recommends irtt for UDP measurements and says its server must run on target hosts.checked 4 Oct 2026
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